[PATCH 2/4][DISCO] shiftfs: rework and extend
Tyler Hicks
tyhicks at canonical.com
Fri Mar 29 22:43:50 UTC 2019
Wew... there's a lot here to review. Patch 1 implements a filesystem and
patch 2 reimplements it and adds a bunch more. :)
I've just got one question below for now.
On 2019-03-27 15:11:26, Christian Brauner wrote:
> From: Christian Brauner <christian at brauner.io>
>
> /* Introduction */
> The shiftfs filesystem is implemented as a stacking filesystem. Since it is
> a stacking filesystem it shares concepts with overlayfs and ecryptfs.
> Usually, shiftfs will be stacked upon another filesystem. The filesystem on
> top - shiftfs - is referred to as "upper filesystem" or "overlay" and the
> filesystem it is stacked upon is referred to as "lower filesystem" or
> "underlay".
>
> /* Marked and Unmarked shiftfs mounts */
> To use shiftfs it is necessary that a given mount is marked as shiftable via
> the "mark" mount option. Any mount of shiftfs without the "mark" mount option
> not on top of a shiftfs mount with the "mark" mount option will be refused with
> EPERM.
> After a marked shiftfs mount has been performed other shiftfs mounts
> referencing the marked shiftfs mount can be created. These secondary shiftfs
> mounts are usually what are of interest.
> The marked shiftfs mount will take a reference to the underlying mountpoint of
> the directory it is marking as shiftable. Any unmarked shiftfts mounts
> referencing this marked shifts mount will take a second reference to this
> directory as well. This ensures that the underlying marked shiftfs mount can be
> unmounted thereby dropping the reference to the underlying directory without
> invalidating the mountpoint of said directory since the non-marked shiftfs
> mount still holds another reference to it.
>
> /* Stacking Depth */
> Shiftfs tries to keep the stack as flat as possible to avoid hitting the
> kernel enforced filesystem stacking limit.
>
> /* Permission Model */
> When the mark shiftfs mount is created shiftfs will record the credentials of
> the creator of the super block and stash it in the super block. When other
> non-mark shiftfs mounts are created that reference the mark shiftfs mount they
> will stash another reference to the creators credentials. Before calling into
> the underlying filesystem shiftfs will switch to the creators credentials and
> revert to the original credentials after the underlying filesystem operation
> returns.
>
> /* Mount Options */
> - mark
> When set the mark mount option indicates that the mount in question is
> allowed to be shifted. Since shiftfs it mountable in by user namespace root
> non-initial user namespace this mount options ensures that the system
> administrator has decided that the marked mount is safe to be shifted.
> To mark a mount as shiftable CAP_SYS_ADMIN in the user namespace is required.
> - passthrough={0,1,2,3}
> This mount options functions as a bitmask. When set to a non-zero value
> shiftfs will try to act as an invisible shim sitting on top of the
> underlying filesystem.
> - 1: Shifts will report the filesystem type of the underlay for stat-like
> system calls.
> - 2: Shiftfs will passthrough whitelisted ioctl() to the underlay.
A good chunk of the added complexity here seems to do with supporting
ioctl(). IIUC, you only needed to add file_operations for this reason.
Also, I see that the next patch allows specific btrfs ioctl's through.
Can you or stgraber give a high level description of why LXD needs the
ioctl functionality?
Thanks!
Tyler
> - 3: Shiftfs will both use 1 and 2.
> Note that mount options on a marked mount cannot be changed.
>
> /* Extended Attributes */
> Shiftfs will make sure to translate extended attributes.
>
> /* Inodes Numbers */
> Shiftfs inodes numbers are copied up from the underlying filesystem, i.e.
> shiftfs inode numbers will be identical to the corresponding underlying
> filesystem's inode numbers. This has the advantage that inotify and friends
> should work out of the box.
> (In essence, shiftfs is nothing but a 1:1 mirror of the underlying filesystem's
> dentries and inodes.)
>
> /* Device Support */
> Shiftfs only supports the creation of pipe and socket devices. Character and
> block devices cannot be created through shiftfs.
>
> Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
> Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
> ---
> fs/Kconfig | 10 +
> fs/shiftfs.c | 1847 ++++++++++++++++++++++++++++++++++++++++----------
> 2 files changed, 1488 insertions(+), 369 deletions(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 22e2e0feba0c..7b9ba073d403 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -121,6 +121,16 @@ config SHIFT_FS
> unprivileged containers can use this to mount root volumes
> using this technique.
>
> +config SHIFT_FS_POSIX_ACL
> + bool "shiftfs POSIX Access Control Lists"
> + depends on SHIFT_FS
> + select FS_POSIX_ACL
> + help
> + POSIX Access Control Lists (ACLs) support permissions for users and
> + groups beyond the owner/group/world scheme.
> +
> + If you don't know what Access Control Lists are, say N.
> +
> menu "Caches"
>
> source "fs/fscache/Kconfig"
> diff --git a/fs/shiftfs.c b/fs/shiftfs.c
> index f7cada126daa..234af4e31736 100644
> --- a/fs/shiftfs.c
> +++ b/fs/shiftfs.c
> @@ -1,3 +1,4 @@
> +#include <linux/capability.h>
> #include <linux/cred.h>
> #include <linux/mount.h>
> #include <linux/file.h>
> @@ -7,83 +8,179 @@
> #include <linux/kernel.h>
> #include <linux/magic.h>
> #include <linux/parser.h>
> +#include <linux/security.h>
> #include <linux/seq_file.h>
> #include <linux/statfs.h>
> #include <linux/slab.h>
> #include <linux/user_namespace.h>
> #include <linux/uidgid.h>
> #include <linux/xattr.h>
> +#include <linux/posix_acl.h>
> +#include <linux/posix_acl_xattr.h>
> +#include <linux/uio.h>
>
> struct shiftfs_super_info {
> struct vfsmount *mnt;
> struct user_namespace *userns;
> + /* creds of process who created the super block */
> + const struct cred *creator_cred;
> bool mark;
> + unsigned int passthrough;
> + struct shiftfs_super_info *info_mark;
> };
>
> -static struct inode *shiftfs_new_inode(struct super_block *sb, umode_t mode,
> - struct dentry *dentry);
> +struct shiftfs_file_info {
> + struct path realpath;
> + struct file *realfile;
> +};
> +
> +struct kmem_cache *shiftfs_file_info_cache;
> +
> +static void shiftfs_fill_inode(struct inode *inode, unsigned long ino,
> + umode_t mode, dev_t dev, struct dentry *dentry);
> +
> +#define SHIFTFS_PASSTHROUGH_NONE 0
> +#define SHIFTFS_PASSTHROUGH_STAT 1
> +#define SHIFTFS_PASSTHROUGH_ALL (SHIFTFS_PASSTHROUGH_STAT)
> +
> +static inline bool shiftfs_passthrough_statfs(struct shiftfs_super_info *info)
> +{
> + if (!(info->passthrough & SHIFTFS_PASSTHROUGH_STAT))
> + return false;
> +
> + if (info->info_mark &&
> + !(info->info_mark->passthrough & SHIFTFS_PASSTHROUGH_STAT))
> + return false;
> +
> + return true;
> +}
>
> enum {
> OPT_MARK,
> + OPT_PASSTHROUGH,
> OPT_LAST,
> };
>
> /* global filesystem options */
> static const match_table_t tokens = {
> { OPT_MARK, "mark" },
> + { OPT_PASSTHROUGH, "passthrough=%u" },
> { OPT_LAST, NULL }
> };
>
> -static const struct cred *shiftfs_get_up_creds(struct super_block *sb)
> +static const struct cred *shiftfs_override_creds(const struct super_block *sb)
> {
> - struct shiftfs_super_info *ssi = sb->s_fs_info;
> - struct cred *cred = prepare_creds();
> + struct shiftfs_super_info *sbinfo = sb->s_fs_info;
>
> - if (!cred)
> - return NULL;
> + return override_creds(sbinfo->creator_cred);
> +}
> +
> +static inline void shiftfs_revert_object_creds(const struct cred *oldcred,
> + struct cred *newcred)
> +{
> + revert_creds(oldcred);
> + put_cred(newcred);
> +}
> +
> +static int shiftfs_override_object_creds(const struct super_block *sb,
> + const struct cred **oldcred,
> + struct cred **newcred,
> + struct dentry *dentry, umode_t mode,
> + bool hardlink)
> +{
> + kuid_t fsuid = current_fsuid();
> + kgid_t fsgid = current_fsgid();
> +
> + *oldcred = shiftfs_override_creds(sb);
> +
> + *newcred = prepare_creds();
> + if (!*newcred) {
> + revert_creds(*oldcred);
> + return -ENOMEM;
> + }
> +
> + (*newcred)->fsuid = KUIDT_INIT(from_kuid(sb->s_user_ns, fsuid));
> + (*newcred)->fsgid = KGIDT_INIT(from_kgid(sb->s_user_ns, fsgid));
> +
> + if (!hardlink) {
> + int err = security_dentry_create_files_as(dentry, mode,
> + &dentry->d_name,
> + *oldcred, *newcred);
> + if (err) {
> + shiftfs_revert_object_creds(*oldcred, *newcred);
> + return err;
> + }
> + }
>
> - cred->fsuid = KUIDT_INIT(from_kuid(sb->s_user_ns, cred->fsuid));
> - cred->fsgid = KGIDT_INIT(from_kgid(sb->s_user_ns, cred->fsgid));
> - put_user_ns(cred->user_ns);
> - cred->user_ns = get_user_ns(ssi->userns);
> + put_cred(override_creds(*newcred));
> + return 0;
> +}
>
> - return cred;
> +static kuid_t shift_kuid(struct user_namespace *from, struct user_namespace *to,
> + kuid_t kuid)
> +{
> + uid_t uid = from_kuid(from, kuid);
> + return make_kuid(to, uid);
> }
>
> -static const struct cred *shiftfs_new_creds(const struct cred **newcred,
> - struct super_block *sb)
> +static kgid_t shift_kgid(struct user_namespace *from, struct user_namespace *to,
> + kgid_t kgid)
> {
> - const struct cred *cred = shiftfs_get_up_creds(sb);
> + gid_t gid = from_kgid(from, kgid);
> + return make_kgid(to, gid);
> +}
>
> - *newcred = cred;
> +static void shiftfs_copyattr(struct inode *from, struct inode *to)
> +{
> + struct user_namespace *from_ns = from->i_sb->s_user_ns;
> + struct user_namespace *to_ns = to->i_sb->s_user_ns;
> +
> + to->i_uid = shift_kuid(from_ns, to_ns, from->i_uid);
> + to->i_gid = shift_kgid(from_ns, to_ns, from->i_gid);
> + to->i_mode = from->i_mode;
> + to->i_atime = from->i_atime;
> + to->i_mtime = from->i_mtime;
> + to->i_ctime = from->i_ctime;
> + i_size_write(to, i_size_read(from));
> +}
>
> - if (cred)
> - cred = override_creds(cred);
> - else
> - printk(KERN_ERR "shiftfs: Credential override failed: no memory\n");
> +static void shiftfs_copyflags(struct inode *from, struct inode *to)
> +{
> + unsigned int mask = S_SYNC | S_IMMUTABLE | S_APPEND | S_NOATIME;
>
> - return cred;
> + inode_set_flags(to, from->i_flags & mask, mask);
> }
>
> -static void shiftfs_old_creds(const struct cred *oldcred,
> - const struct cred **newcred)
> +static void shiftfs_file_accessed(struct file *file)
> {
> - if (!*newcred)
> + struct inode *upperi, *loweri;
> +
> + if (file->f_flags & O_NOATIME)
> return;
>
> - revert_creds(oldcred);
> - put_cred(*newcred);
> + upperi = file_inode(file);
> + loweri = upperi->i_private;
> +
> + if (!loweri)
> + return;
> +
> + upperi->i_mtime = loweri->i_mtime;
> + upperi->i_ctime = loweri->i_ctime;
> +
> + touch_atime(&file->f_path);
> }
>
> -static int shiftfs_parse_options(struct shiftfs_super_info *ssi, char *options)
> +static int shiftfs_parse_mount_options(struct shiftfs_super_info *sbinfo,
> + char *options)
> {
> char *p;
> substring_t args[MAX_OPT_ARGS];
>
> - ssi->mark = false;
> + sbinfo->mark = false;
> + sbinfo->passthrough = 0;
>
> while ((p = strsep(&options, ",")) != NULL) {
> - int token;
> + int err, intarg, token;
>
> if (!*p)
> continue;
> @@ -91,121 +188,140 @@ static int shiftfs_parse_options(struct shiftfs_super_info *ssi, char *options)
> token = match_token(p, tokens, args);
> switch (token) {
> case OPT_MARK:
> - ssi->mark = true;
> + sbinfo->mark = true;
> + break;
> + case OPT_PASSTHROUGH:
> + err = match_int(&args[0], &intarg);
> + if (err)
> + return err;
> +
> + if (intarg & ~SHIFTFS_PASSTHROUGH_ALL)
> + return -EINVAL;
> +
> + sbinfo->passthrough = intarg;
> break;
> default:
> return -EINVAL;
> }
> }
> +
> return 0;
> }
>
> static void shiftfs_d_release(struct dentry *dentry)
> {
> - struct dentry *real = dentry->d_fsdata;
> + struct dentry *lowerd = dentry->d_fsdata;
>
> - dput(real);
> + if (lowerd)
> + dput(lowerd);
> }
>
> static struct dentry *shiftfs_d_real(struct dentry *dentry,
> const struct inode *inode)
> {
> - struct dentry *real = dentry->d_fsdata;
> + struct dentry *lowerd = dentry->d_fsdata;
> +
> + if (inode && d_inode(dentry) == inode)
> + return dentry;
>
> - if (unlikely(real->d_flags & DCACHE_OP_REAL))
> - return real->d_op->d_real(real, real->d_inode);
> + lowerd = d_real(lowerd, inode);
> + if (lowerd && (!inode || inode == d_inode(lowerd)))
> + return lowerd;
>
> - return real;
> + WARN(1, "shiftfs_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
> + inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
> + return dentry;
> }
>
> static int shiftfs_d_weak_revalidate(struct dentry *dentry, unsigned int flags)
> {
> - struct dentry *real = dentry->d_fsdata;
> + int err = 1;
> + struct dentry *lowerd = dentry->d_fsdata;
>
> - if (d_unhashed(real))
> + if (d_is_negative(lowerd) != d_is_negative(dentry))
> return 0;
>
> - if (!(real->d_flags & DCACHE_OP_WEAK_REVALIDATE))
> - return 1;
> + if ((lowerd->d_flags & DCACHE_OP_WEAK_REVALIDATE))
> + err = lowerd->d_op->d_weak_revalidate(lowerd, flags);
>
> - return real->d_op->d_weak_revalidate(real, flags);
> + if (d_really_is_positive(dentry)) {
> + struct inode *inode = d_inode(dentry);
> + struct inode *loweri = d_inode(lowerd);
> +
> + shiftfs_copyattr(loweri, inode);
> + if (!inode->i_nlink)
> + err = 0;
> + }
> +
> + return err;
> }
>
> static int shiftfs_d_revalidate(struct dentry *dentry, unsigned int flags)
> {
> - struct dentry *real = dentry->d_fsdata;
> - int ret;
> + int err = 1;
> + struct dentry *lowerd = dentry->d_fsdata;
>
> - if (d_unhashed(real))
> + if (d_unhashed(lowerd) ||
> + ((d_is_negative(lowerd) != d_is_negative(dentry))))
> return 0;
>
> - /*
> - * inode state of underlying changed from positive to negative
> - * or vice versa; force a lookup to update our view
> - */
> - if (d_is_negative(real) != d_is_negative(dentry))
> - return 0;
> + if (flags & LOOKUP_RCU)
> + return -ECHILD;
>
> - if (!(real->d_flags & DCACHE_OP_REVALIDATE))
> - return 1;
> + if ((lowerd->d_flags & DCACHE_OP_REVALIDATE))
> + err = lowerd->d_op->d_revalidate(lowerd, flags);
>
> - ret = real->d_op->d_revalidate(real, flags);
> + if (d_really_is_positive(dentry)) {
> + struct inode *inode = d_inode(dentry);
> + struct inode *loweri = d_inode(lowerd);
>
> - if (ret == 0 && !(flags & LOOKUP_RCU))
> - d_invalidate(real);
> + shiftfs_copyattr(loweri, inode);
> + if (!inode->i_nlink)
> + err = 0;
> + }
>
> - return ret;
> + return err;
> }
>
> static const struct dentry_operations shiftfs_dentry_ops = {
> - .d_release = shiftfs_d_release,
> - .d_real = shiftfs_d_real,
> - .d_revalidate = shiftfs_d_revalidate,
> + .d_release = shiftfs_d_release,
> + .d_real = shiftfs_d_real,
> + .d_revalidate = shiftfs_d_revalidate,
> .d_weak_revalidate = shiftfs_d_weak_revalidate,
> };
>
> -static int shiftfs_readlink(struct dentry *dentry, char __user *data,
> - int flags)
> -{
> - struct dentry *real = dentry->d_fsdata;
> - const struct inode_operations *iop = real->d_inode->i_op;
> -
> - if (iop->readlink)
> - return iop->readlink(real, data, flags);
> -
> - return -EINVAL;
> -}
> -
> static const char *shiftfs_get_link(struct dentry *dentry, struct inode *inode,
> struct delayed_call *done)
> {
> - if (dentry) {
> - struct dentry *real = dentry->d_fsdata;
> - struct inode *reali = real->d_inode;
> - const struct inode_operations *iop = reali->i_op;
> - const char *res = ERR_PTR(-EPERM);
> -
> - if (iop->get_link)
> - res = iop->get_link(real, reali, done);
> + const char *p;
> + const struct cred *oldcred;
> + struct dentry *lowerd;
>
> - return res;
> - } else {
> - /* RCU lookup not supported */
> + /* RCU lookup not supported */
> + if (!dentry)
> return ERR_PTR(-ECHILD);
> - }
> +
> + lowerd = dentry->d_fsdata;
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + p = vfs_get_link(lowerd, done);
> + revert_creds(oldcred);
> +
> + return p;
> }
>
> static int shiftfs_setxattr(struct dentry *dentry, struct inode *inode,
> const char *name, const void *value,
> size_t size, int flags)
> {
> - struct dentry *real = dentry->d_fsdata;
> - int err = -EOPNOTSUPP;
> - const struct cred *oldcred, *newcred;
> + struct dentry *lowerd = dentry->d_fsdata;
> + int err;
> + const struct cred *oldcred;
> +
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + err = vfs_setxattr(lowerd, name, value, size, flags);
> + revert_creds(oldcred);
>
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> - err = vfs_setxattr(real, name, value, size, flags);
> - shiftfs_old_creds(oldcred, &newcred);
> + shiftfs_copyattr(lowerd->d_inode, inode);
>
> return err;
> }
> @@ -214,13 +330,13 @@ static int shiftfs_xattr_get(const struct xattr_handler *handler,
> struct dentry *dentry, struct inode *inode,
> const char *name, void *value, size_t size)
> {
> - struct dentry *real = dentry->d_fsdata;
> + struct dentry *lowerd = dentry->d_fsdata;
> int err;
> - const struct cred *oldcred, *newcred;
> + const struct cred *oldcred;
>
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> - err = vfs_getxattr(real, name, value, size);
> - shiftfs_old_creds(oldcred, &newcred);
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + err = vfs_getxattr(lowerd, name, value, size);
> + revert_creds(oldcred);
>
> return err;
> }
> @@ -228,26 +344,29 @@ static int shiftfs_xattr_get(const struct xattr_handler *handler,
> static ssize_t shiftfs_listxattr(struct dentry *dentry, char *list,
> size_t size)
> {
> - struct dentry *real = dentry->d_fsdata;
> + struct dentry *lowerd = dentry->d_fsdata;
> int err;
> - const struct cred *oldcred, *newcred;
> + const struct cred *oldcred;
>
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> - err = vfs_listxattr(real, list, size);
> - shiftfs_old_creds(oldcred, &newcred);
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + err = vfs_listxattr(lowerd, list, size);
> + revert_creds(oldcred);
>
> return err;
> }
>
> static int shiftfs_removexattr(struct dentry *dentry, const char *name)
> {
> - struct dentry *real = dentry->d_fsdata;
> + struct dentry *lowerd = dentry->d_fsdata;
> int err;
> - const struct cred *oldcred, *newcred;
> + const struct cred *oldcred;
> +
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + err = vfs_removexattr(lowerd, name);
> + revert_creds(oldcred);
>
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> - err = vfs_removexattr(real, name);
> - shiftfs_old_creds(oldcred, &newcred);
> + /* update c/mtime */
> + shiftfs_copyattr(lowerd->d_inode, d_inode(dentry));
>
> return err;
> }
> @@ -262,93 +381,157 @@ static int shiftfs_xattr_set(const struct xattr_handler *handler,
> return shiftfs_setxattr(dentry, inode, name, value, size, flags);
> }
>
> -static void shiftfs_fill_inode(struct inode *inode, struct dentry *dentry)
> +static int shiftfs_inode_test(struct inode *inode, void *data)
> {
> - struct inode *reali;
> -
> - if (!dentry)
> - return;
> -
> - reali = dentry->d_inode;
> -
> - if (!reali->i_op->get_link)
> - inode->i_opflags |= IOP_NOFOLLOW;
> + return inode->i_private == data;
> +}
>
> - inode->i_mapping = reali->i_mapping;
> - inode->i_private = dentry;
> +static int shiftfs_inode_set(struct inode *inode, void *data)
> +{
> + inode->i_private = data;
> + return 0;
> }
>
> -static int shiftfs_make_object(struct inode *dir, struct dentry *dentry,
> - umode_t mode, const char *symlink,
> - struct dentry *hardlink, bool excl)
> +static int shiftfs_create_object(struct inode *diri, struct dentry *dentry,
> + umode_t mode, const char *symlink,
> + struct dentry *hardlink, bool excl)
> {
> - struct dentry *real = dir->i_private, *new = dentry->d_fsdata;
> - struct inode *reali = real->d_inode, *newi;
> - const struct inode_operations *iop = reali->i_op;
> int err;
> - const struct cred *oldcred, *newcred;
> - bool op_ok = false;
> + const struct cred *oldcred;
> + struct cred *newcred;
> + void *loweri_iop_ptr = NULL;
> + umode_t modei = mode;
> + struct super_block *dir_sb = diri->i_sb;
> + struct dentry *lowerd_new = dentry->d_fsdata;
> + struct inode *inode = NULL, *loweri_dir = diri->i_private;
> + const struct inode_operations *loweri_dir_iop = loweri_dir->i_op;
> + struct dentry *lowerd_link = NULL;
>
> if (hardlink) {
> - op_ok = iop->link;
> + loweri_iop_ptr = loweri_dir_iop->link;
> } else {
> switch (mode & S_IFMT) {
> case S_IFDIR:
> - op_ok = iop->mkdir;
> + loweri_iop_ptr = loweri_dir_iop->mkdir;
> break;
> case S_IFREG:
> - op_ok = iop->create;
> + loweri_iop_ptr = loweri_dir_iop->create;
> break;
> case S_IFLNK:
> - op_ok = iop->symlink;
> + loweri_iop_ptr = loweri_dir_iop->symlink;
> + break;
> + case S_IFSOCK:
> + /* fall through */
> + case S_IFIFO:
> + loweri_iop_ptr = loweri_dir_iop->mknod;
> + break;
> }
> }
> - if (!op_ok)
> - return -EINVAL;
> + if (!loweri_iop_ptr) {
> + err = -EINVAL;
> + goto out_iput;
> + }
>
> + inode_lock_nested(loweri_dir, I_MUTEX_PARENT);
>
> - newi = shiftfs_new_inode(dentry->d_sb, mode, NULL);
> - if (!newi)
> - return -ENOMEM;
> + if (!hardlink) {
> + inode = new_inode(dir_sb);
> + if (!inode) {
> + err = -ENOMEM;
> + goto out_iput;
> + }
> +
> + /*
> + * new_inode() will have added the new inode to the super
> + * block's list of inodes. Further below we will call
> + * inode_insert5() Which would perform the same operation again
> + * thereby corrupting the list. To avoid this raise I_CREATING
> + * in i_state which will cause inode_insert5() to skip this
> + * step. I_CREATING will be cleared by d_instantiate_new()
> + * below.
> + */
> + spin_lock(&inode->i_lock);
> + inode->i_state |= I_CREATING;
> + spin_unlock(&inode->i_lock);
>
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> + inode_init_owner(inode, diri, mode);
> + modei = inode->i_mode;
> + }
>
> - inode_lock_nested(reali, I_MUTEX_PARENT);
> + err = shiftfs_override_object_creds(dentry->d_sb, &oldcred, &newcred,
> + dentry, modei, hardlink != NULL);
> + if (err)
> + goto out_iput;
>
> - err = -EINVAL; /* shut gcc up about uninit var */
> if (hardlink) {
> - struct dentry *realhardlink = hardlink->d_fsdata;
> -
> - err = vfs_link(realhardlink, reali, new, NULL);
> + lowerd_link = hardlink->d_fsdata;
> + err = vfs_link(lowerd_link, loweri_dir, lowerd_new, NULL);
> } else {
> - switch (mode & S_IFMT) {
> + switch (modei & S_IFMT) {
> case S_IFDIR:
> - err = vfs_mkdir(reali, new, mode);
> + err = vfs_mkdir(loweri_dir, lowerd_new, modei);
> break;
> case S_IFREG:
> - err = vfs_create(reali, new, mode, excl);
> + err = vfs_create(loweri_dir, lowerd_new, modei, excl);
> break;
> case S_IFLNK:
> - err = vfs_symlink(reali, new, symlink);
> + err = vfs_symlink(loweri_dir, lowerd_new, symlink);
> + break;
> + case S_IFSOCK:
> + /* fall through */
> + case S_IFIFO:
> + err = vfs_mknod(loweri_dir, lowerd_new, modei, 0);
> + break;
> + default:
> + err = -EINVAL;
> + break;
> }
> }
>
> - shiftfs_old_creds(oldcred, &newcred);
> + shiftfs_revert_object_creds(oldcred, newcred);
>
> + if (!err && WARN_ON(!lowerd_new->d_inode))
> + err = -EIO;
> if (err)
> - goto out_dput;
> + goto out_iput;
> +
> + if (hardlink) {
> + inode = d_inode(hardlink);
> + ihold(inode);
> +
> + /* copy up times from lower inode */
> + shiftfs_copyattr(d_inode(lowerd_link), inode);
> + set_nlink(d_inode(hardlink), d_inode(lowerd_link)->i_nlink);
> + d_instantiate(dentry, inode);
> + } else {
> + struct inode *inode_tmp;
> + struct inode *loweri_new = d_inode(lowerd_new);
> +
> + inode_tmp = inode_insert5(inode, (unsigned long)loweri_new,
> + shiftfs_inode_test, shiftfs_inode_set,
> + loweri_new);
> + if (unlikely(inode_tmp != inode)) {
> + pr_err_ratelimited("shiftfs: newly created inode found in cache\n");
> + iput(inode_tmp);
> + err = -EINVAL;
> + goto out_iput;
> + }
>
> - shiftfs_fill_inode(newi, new);
> + ihold(loweri_new);
> + shiftfs_fill_inode(inode, loweri_new->i_ino, loweri_new->i_mode,
> + 0, lowerd_new);
> + d_instantiate_new(dentry, inode);
> + }
>
> - d_instantiate(dentry, newi);
> + shiftfs_copyattr(loweri_dir, diri);
> + if (loweri_iop_ptr == loweri_dir_iop->mkdir)
> + set_nlink(diri, loweri_dir->i_nlink);
>
> - new = NULL;
> - newi = NULL;
> + inode = NULL;
>
> - out_dput:
> - dput(new);
> - iput(newi);
> - inode_unlock(reali);
> +out_iput:
> + iput(inode);
> + inode_unlock(loweri_dir);
>
> return err;
> }
> @@ -358,7 +541,7 @@ static int shiftfs_create(struct inode *dir, struct dentry *dentry,
> {
> mode |= S_IFREG;
>
> - return shiftfs_make_object(dir, dentry, mode, NULL, NULL, excl);
> + return shiftfs_create_object(dir, dentry, mode, NULL, NULL, excl);
> }
>
> static int shiftfs_mkdir(struct inode *dir, struct dentry *dentry,
> @@ -366,39 +549,52 @@ static int shiftfs_mkdir(struct inode *dir, struct dentry *dentry,
> {
> mode |= S_IFDIR;
>
> - return shiftfs_make_object(dir, dentry, mode, NULL, NULL, false);
> + return shiftfs_create_object(dir, dentry, mode, NULL, NULL, false);
> }
>
> static int shiftfs_link(struct dentry *hardlink, struct inode *dir,
> struct dentry *dentry)
> {
> - return shiftfs_make_object(dir, dentry, 0, NULL, hardlink, false);
> + return shiftfs_create_object(dir, dentry, 0, NULL, hardlink, false);
> +}
> +
> +static int shiftfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
> + dev_t rdev)
> +{
> + if (S_ISCHR(mode) || S_ISBLK(mode))
> + return -EPERM;
> +
> + return shiftfs_create_object(dir, dentry, mode, NULL, NULL, false);
> }
>
> static int shiftfs_symlink(struct inode *dir, struct dentry *dentry,
> const char *symlink)
> {
> - return shiftfs_make_object(dir, dentry, S_IFLNK, symlink, NULL, false);
> + return shiftfs_create_object(dir, dentry, S_IFLNK, symlink, NULL, false);
> }
>
> static int shiftfs_rm(struct inode *dir, struct dentry *dentry, bool rmdir)
> {
> - struct dentry *real = dir->i_private, *new = dentry->d_fsdata;
> - struct inode *reali = real->d_inode;
> + struct dentry *lowerd = dentry->d_fsdata;
> + struct inode *loweri = dir->i_private;
> int err;
> - const struct cred *oldcred, *newcred;
> -
> - inode_lock_nested(reali, I_MUTEX_PARENT);
> -
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> + const struct cred *oldcred;
>
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + inode_lock_nested(loweri, I_MUTEX_PARENT);
> if (rmdir)
> - err = vfs_rmdir(reali, new);
> + err = vfs_rmdir(loweri, lowerd);
> else
> - err = vfs_unlink(reali, new, NULL);
> + err = vfs_unlink(loweri, lowerd, NULL);
> + inode_unlock(loweri);
> + revert_creds(oldcred);
>
> - shiftfs_old_creds(oldcred, &newcred);
> - inode_unlock(reali);
> + shiftfs_copyattr(loweri, dir);
> + set_nlink(d_inode(dentry), loweri->i_nlink);
> + if (!err)
> + d_drop(dentry);
> +
> + set_nlink(dir, loweri->i_nlink);
>
> return err;
> }
> @@ -417,27 +613,30 @@ static int shiftfs_rename(struct inode *olddir, struct dentry *old,
> struct inode *newdir, struct dentry *new,
> unsigned int flags)
> {
> - struct dentry *rodd = olddir->i_private, *rndd = newdir->i_private,
> - *realold = old->d_fsdata,
> - *realnew = new->d_fsdata, *trap;
> - struct inode *realolddir = rodd->d_inode, *realnewdir = rndd->d_inode;
> + struct dentry *lowerd_dir_old = old->d_parent->d_fsdata,
> + *lowerd_dir_new = new->d_parent->d_fsdata,
> + *lowerd_old = old->d_fsdata, *lowerd_new = new->d_fsdata,
> + *trapd;
> + struct inode *loweri_dir_old = lowerd_dir_old->d_inode,
> + *loweri_dir_new = lowerd_dir_new->d_inode;
> int err = -EINVAL;
> - const struct cred *oldcred, *newcred;
> + const struct cred *oldcred;
>
> - trap = lock_rename(rndd, rodd);
> + trapd = lock_rename(lowerd_dir_new, lowerd_dir_old);
>
> - if (trap == realold || trap == realnew)
> + if (trapd == lowerd_old || trapd == lowerd_new)
> goto out_unlock;
>
> - oldcred = shiftfs_new_creds(&newcred, old->d_sb);
> -
> - err = vfs_rename(realolddir, realold, realnewdir,
> - realnew, NULL, flags);
> + oldcred = shiftfs_override_creds(old->d_sb);
> + err = vfs_rename(loweri_dir_old, lowerd_old, loweri_dir_new, lowerd_new,
> + NULL, flags);
> + revert_creds(oldcred);
>
> - shiftfs_old_creds(oldcred, &newcred);
> + shiftfs_copyattr(loweri_dir_old, olddir);
> + shiftfs_copyattr(loweri_dir_new, newdir);
>
> - out_unlock:
> - unlock_rename(rndd, rodd);
> +out_unlock:
> + unlock_rename(lowerd_dir_new, lowerd_dir_old);
>
> return err;
> }
> @@ -445,304 +644,1205 @@ static int shiftfs_rename(struct inode *olddir, struct dentry *old,
> static struct dentry *shiftfs_lookup(struct inode *dir, struct dentry *dentry,
> unsigned int flags)
> {
> - struct dentry *real = dir->i_private, *new;
> - struct inode *reali = real->d_inode, *newi;
> - const struct cred *oldcred, *newcred;
> -
> - inode_lock(reali);
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> - new = lookup_one_len(dentry->d_name.name, real, dentry->d_name.len);
> - shiftfs_old_creds(oldcred, &newcred);
> - inode_unlock(reali);
> + struct dentry *new;
> + struct inode *newi;
> + const struct cred *oldcred;
> + struct dentry *lowerd = dentry->d_parent->d_fsdata;
> + struct inode *inode = NULL, *loweri = lowerd->d_inode;
> +
> + inode_lock(loweri);
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + new = lookup_one_len(dentry->d_name.name, lowerd, dentry->d_name.len);
> + revert_creds(oldcred);
> + inode_unlock(loweri);
>
> if (IS_ERR(new))
> return new;
>
> dentry->d_fsdata = new;
>
> - newi = NULL;
> - if (!new->d_inode)
> + newi = new->d_inode;
> + if (!newi)
> goto out;
>
> - newi = shiftfs_new_inode(dentry->d_sb, new->d_inode->i_mode, new);
> - if (!newi) {
> + inode = iget5_locked(dentry->d_sb, (unsigned long)newi,
> + shiftfs_inode_test, shiftfs_inode_set, newi);
> + if (!inode) {
> dput(new);
> return ERR_PTR(-ENOMEM);
> }
> + if (inode->i_state & I_NEW) {
> + /*
> + * inode->i_private set by shiftfs_inode_set(), but we still
> + * need to take a reference
> + */
> + ihold(newi);
> + shiftfs_fill_inode(inode, newi->i_ino, newi->i_mode, 0, new);
> + unlock_new_inode(inode);
> + }
>
> - out:
> - return d_splice_alias(newi, dentry);
> +out:
> + return d_splice_alias(inode, dentry);
> }
>
> static int shiftfs_permission(struct inode *inode, int mask)
> {
> - struct dentry *real = inode->i_private;
> - struct inode *reali = real->d_inode;
> - const struct inode_operations *iop = reali->i_op;
> int err;
> - const struct cred *oldcred, *newcred;
> + const struct cred *oldcred;
> + struct inode *loweri = inode->i_private;
>
> - if (mask & MAY_NOT_BLOCK)
> + if (!loweri) {
> + WARN_ON(!(mask & MAY_NOT_BLOCK));
> return -ECHILD;
> + }
>
> - oldcred = shiftfs_new_creds(&newcred, inode->i_sb);
> - if (iop->permission)
> - err = iop->permission(reali, mask);
> - else
> - err = generic_permission(reali, mask);
> - shiftfs_old_creds(oldcred, &newcred);
> + err = generic_permission(inode, mask);
> + if (err)
> + return err;
> +
> + oldcred = shiftfs_override_creds(inode->i_sb);
> + err = inode_permission(loweri, mask);
> + revert_creds(oldcred);
> +
> + return err;
> +}
> +
> +static int shiftfs_fiemap(struct inode *inode,
> + struct fiemap_extent_info *fieinfo, u64 start,
> + u64 len)
> +{
> + int err;
> + const struct cred *oldcred;
> + struct inode *loweri = inode->i_private;
> +
> + if (!loweri->i_op->fiemap)
> + return -EOPNOTSUPP;
> +
> + oldcred = shiftfs_override_creds(inode->i_sb);
> + if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC)
> + filemap_write_and_wait(loweri->i_mapping);
> + err = loweri->i_op->fiemap(loweri, fieinfo, start, len);
> + revert_creds(oldcred);
> +
> + return err;
> +}
> +
> +static int shiftfs_tmpfile(struct inode *dir, struct dentry *dentry,
> + umode_t mode)
> +{
> + int err;
> + const struct cred *oldcred;
> + struct dentry *lowerd = dentry->d_fsdata;
> + struct inode *loweri = dir->i_private;
> +
> + if (!loweri->i_op->tmpfile)
> + return -EOPNOTSUPP;
> +
> + oldcred = shiftfs_override_creds(dir->i_sb);
> + err = loweri->i_op->tmpfile(loweri, lowerd, mode);
> + revert_creds(oldcred);
>
> return err;
> }
>
> static int shiftfs_setattr(struct dentry *dentry, struct iattr *attr)
> {
> - struct dentry *real = dentry->d_fsdata;
> - struct inode *reali = real->d_inode;
> - const struct inode_operations *iop = reali->i_op;
> + struct dentry *lowerd = dentry->d_fsdata;
> + struct inode *loweri = lowerd->d_inode;
> struct iattr newattr = *attr;
> - const struct cred *oldcred, *newcred;
> + const struct cred *oldcred;
> struct super_block *sb = dentry->d_sb;
> int err;
>
> + err = setattr_prepare(dentry, attr);
> + if (err)
> + return err;
> +
> newattr.ia_uid = KUIDT_INIT(from_kuid(sb->s_user_ns, attr->ia_uid));
> newattr.ia_gid = KGIDT_INIT(from_kgid(sb->s_user_ns, attr->ia_gid));
>
> - oldcred = shiftfs_new_creds(&newcred, dentry->d_sb);
> - inode_lock(reali);
> - if (iop->setattr)
> - err = iop->setattr(real, &newattr);
> - else
> - err = simple_setattr(real, &newattr);
> - inode_unlock(reali);
> - shiftfs_old_creds(oldcred, &newcred);
> + inode_lock(loweri);
> + oldcred = shiftfs_override_creds(dentry->d_sb);
> + err = notify_change(lowerd, attr, NULL);
> + revert_creds(oldcred);
> + inode_unlock(loweri);
>
> - if (err)
> - return err;
> + shiftfs_copyattr(loweri, d_inode(dentry));
>
> - /* all OK, reflect the change on our inode */
> - setattr_copy(d_inode(dentry), attr);
> - return 0;
> + return err;
> }
>
> static int shiftfs_getattr(const struct path *path, struct kstat *stat,
> u32 request_mask, unsigned int query_flags)
> {
> struct inode *inode = path->dentry->d_inode;
> - struct dentry *real = path->dentry->d_fsdata;
> - struct inode *reali = real->d_inode;
> - const struct inode_operations *iop = reali->i_op;
> - struct path newpath = { .mnt = path->dentry->d_sb->s_fs_info, .dentry = real };
> - int err = 0;
> -
> - if (iop->getattr)
> - err = iop->getattr(&newpath, stat, request_mask, query_flags);
> - else
> - generic_fillattr(reali, stat);
> + struct dentry *lowerd = path->dentry->d_fsdata;
> + struct inode *loweri = lowerd->d_inode;
> + struct shiftfs_super_info *info = path->dentry->d_sb->s_fs_info;
> + struct path newpath = { .mnt = info->mnt, .dentry = lowerd };
> + struct user_namespace *from_ns = loweri->i_sb->s_user_ns;
> + struct user_namespace *to_ns = inode->i_sb->s_user_ns;
> + const struct cred *oldcred;
> + int err;
> +
> + oldcred = shiftfs_override_creds(inode->i_sb);
> + err = vfs_getattr(&newpath, stat, request_mask, query_flags);
> + revert_creds(oldcred);
>
> if (err)
> return err;
>
> /* transform the underlying id */
> - stat->uid = make_kuid(inode->i_sb->s_user_ns, __kuid_val(stat->uid));
> - stat->gid = make_kgid(inode->i_sb->s_user_ns, __kgid_val(stat->gid));
> + stat->uid = shift_kuid(from_ns, to_ns, stat->uid);
> + stat->gid = shift_kgid(from_ns, to_ns, stat->gid);
> return 0;
> }
>
> -static const struct inode_operations shiftfs_inode_ops = {
> - .lookup = shiftfs_lookup,
> - .getattr = shiftfs_getattr,
> - .setattr = shiftfs_setattr,
> - .permission = shiftfs_permission,
> - .mkdir = shiftfs_mkdir,
> - .symlink = shiftfs_symlink,
> - .get_link = shiftfs_get_link,
> - .readlink = shiftfs_readlink,
> - .unlink = shiftfs_unlink,
> - .rmdir = shiftfs_rmdir,
> - .rename = shiftfs_rename,
> - .link = shiftfs_link,
> - .create = shiftfs_create,
> - .mknod = NULL, /* no special files currently */
> - .listxattr = shiftfs_listxattr,
> -};
> +#ifdef CONFIG_SHIFT_FS_POSIX_ACL
>
> -static struct inode *shiftfs_new_inode(struct super_block *sb, umode_t mode,
> - struct dentry *dentry)
> +static int
> +shift_acl_ids(struct user_namespace *from, struct user_namespace *to,
> + struct posix_acl *acl)
> {
> - struct inode *inode;
> -
> - inode = new_inode(sb);
> - if (!inode)
> - return NULL;
> -
> - /*
> - * our inode is completely vestigial. All lookups, getattr
> - * and permission checks are done on the underlying inode, so
> - * what the user sees is entirely from the underlying inode.
> - */
> - mode &= S_IFMT;
> + int i;
> +
> + for (i = 0; i < acl->a_count; i++) {
> + struct posix_acl_entry *e = &acl->a_entries[i];
> + switch(e->e_tag) {
> + case ACL_USER:
> + e->e_uid = shift_kuid(from, to, e->e_uid);
> + if (!uid_valid(e->e_uid))
> + return -EOVERFLOW;
> + break;
> + case ACL_GROUP:
> + e->e_gid = shift_kgid(from, to, e->e_gid);
> + if (!gid_valid(e->e_gid))
> + return -EOVERFLOW;
> + break;
> + }
> + }
> + return 0;
> +}
>
> - inode->i_ino = get_next_ino();
> - inode->i_mode = mode;
> - inode->i_flags |= S_NOATIME | S_NOCMTIME;
> +static void
> +shift_acl_xattr_ids(struct user_namespace *from, struct user_namespace *to,
> + void *value, size_t size)
> +{
> + struct posix_acl_xattr_header *header = value;
> + struct posix_acl_xattr_entry *entry = (void *)(header + 1), *end;
> + int count;
> + kuid_t kuid;
> + kgid_t kgid;
>
> - inode->i_op = &shiftfs_inode_ops;
> + if (!value)
> + return;
> + if (size < sizeof(struct posix_acl_xattr_header))
> + return;
> + if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
> + return;
>
> - shiftfs_fill_inode(inode, dentry);
> + count = posix_acl_xattr_count(size);
> + if (count < 0)
> + return;
> + if (count == 0)
> + return;
>
> - return inode;
> + for (end = entry + count; entry != end; entry++) {
> + switch(le16_to_cpu(entry->e_tag)) {
> + case ACL_USER:
> + kuid = make_kuid(&init_user_ns, le32_to_cpu(entry->e_id));
> + kuid = shift_kuid(from, to, kuid);
> + entry->e_id = cpu_to_le32(from_kuid(&init_user_ns, kuid));
> + break;
> + case ACL_GROUP:
> + kgid = make_kgid(&init_user_ns, le32_to_cpu(entry->e_id));
> + kgid = shift_kgid(from, to, kgid);
> + entry->e_id = cpu_to_le32(from_kgid(&init_user_ns, kgid));
> + break;
> + default:
> + break;
> + }
> + }
> }
>
> -static int shiftfs_show_options(struct seq_file *m, struct dentry *dentry)
> +static struct posix_acl *shiftfs_get_acl(struct inode *inode, int type)
> {
> - struct super_block *sb = dentry->d_sb;
> - struct shiftfs_super_info *ssi = sb->s_fs_info;
> + struct inode *loweri = inode->i_private;
> + const struct cred *oldcred;
> + struct posix_acl *lower_acl, *acl = NULL;
> + struct user_namespace *from_ns = loweri->i_sb->s_user_ns;
> + struct user_namespace *to_ns = inode->i_sb->s_user_ns;
> + int size;
> + int err;
>
> - if (ssi->mark)
> - seq_show_option(m, "mark", NULL);
> + if (!IS_POSIXACL(loweri))
> + return NULL;
>
> - return 0;
> -}
> + oldcred = shiftfs_override_creds(inode->i_sb);
> + lower_acl = get_acl(loweri, type);
> + revert_creds(oldcred);
>
> -static int shiftfs_statfs(struct dentry *dentry, struct kstatfs *buf)
> -{
> - struct super_block *sb = dentry->d_sb;
> - struct shiftfs_super_info *ssi = sb->s_fs_info;
> - struct dentry *root = sb->s_root;
> - struct dentry *realroot = root->d_fsdata;
> - struct path realpath = { .mnt = ssi->mnt, .dentry = realroot };
> - int err;
> + if (lower_acl && !IS_ERR(lower_acl)) {
> + /* XXX: export posix_acl_clone? */
> + size = sizeof(struct posix_acl) +
> + lower_acl->a_count * sizeof(struct posix_acl_entry);
> + acl = kmemdup(lower_acl, size, GFP_KERNEL);
> + posix_acl_release(lower_acl);
>
> - err = vfs_statfs(&realpath, buf);
> - if (err)
> - return err;
> + if (!acl)
> + return ERR_PTR(-ENOMEM);
>
> - buf->f_type = sb->s_magic;
> + refcount_set(&acl->a_refcount, 1);
>
> - return 0;
> + err = shift_acl_ids(from_ns, to_ns, acl);
> + if (err) {
> + kfree(acl);
> + return ERR_PTR(err);
> + }
> + }
> +
> + return acl;
> }
>
> -static void shiftfs_put_super(struct super_block *sb)
> +static int
> +shiftfs_posix_acl_xattr_get(const struct xattr_handler *handler,
> + struct dentry *dentry, struct inode *inode,
> + const char *name, void *buffer, size_t size)
> {
> - struct shiftfs_super_info *ssi = sb->s_fs_info;
> + struct inode *loweri = inode->i_private;
> + int ret;
> +
> + ret = shiftfs_xattr_get(NULL, dentry, inode, handler->name,
> + buffer, size);
> + if (ret < 0)
> + return ret;
>
> - mntput(ssi->mnt);
> - put_user_ns(ssi->userns);
> - kfree(ssi);
> + inode_lock(loweri);
> + shift_acl_xattr_ids(loweri->i_sb->s_user_ns, inode->i_sb->s_user_ns,
> + buffer, size);
> + inode_unlock(loweri);
> + return ret;
> }
>
> -static const struct xattr_handler shiftfs_xattr_handler = {
> - .prefix = "",
> - .get = shiftfs_xattr_get,
> - .set = shiftfs_xattr_set,
> -};
> +static int
> +shiftfs_posix_acl_xattr_set(const struct xattr_handler *handler,
> + struct dentry *dentry, struct inode *inode,
> + const char *name, const void *value,
> + size_t size, int flags)
> +{
> + struct inode *loweri = inode->i_private;
> + int err;
>
> -const struct xattr_handler *shiftfs_xattr_handlers[] = {
> - &shiftfs_xattr_handler,
> - NULL
> -};
> + if (!IS_POSIXACL(loweri) || !loweri->i_op->set_acl)
> + return -EOPNOTSUPP;
> + if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
> + return value ? -EACCES : 0;
> + if (!inode_owner_or_capable(inode))
> + return -EPERM;
> +
> + if (value) {
> + shift_acl_xattr_ids(inode->i_sb->s_user_ns,
> + loweri->i_sb->s_user_ns,
> + (void *)value, size);
> + err = shiftfs_setxattr(dentry, inode, handler->name, value,
> + size, flags);
> + } else {
> + err = shiftfs_removexattr(dentry, handler->name);
> + }
>
> -static const struct super_operations shiftfs_super_ops = {
> - .put_super = shiftfs_put_super,
> - .show_options = shiftfs_show_options,
> - .statfs = shiftfs_statfs,
> + if (!err)
> + shiftfs_copyattr(loweri, inode);
> +
> + return err;
> +}
> +
> +static const struct xattr_handler
> +shiftfs_posix_acl_access_xattr_handler = {
> + .name = XATTR_NAME_POSIX_ACL_ACCESS,
> + .flags = ACL_TYPE_ACCESS,
> + .get = shiftfs_posix_acl_xattr_get,
> + .set = shiftfs_posix_acl_xattr_set,
> };
>
> -struct shiftfs_data {
> - void *data;
> - const char *path;
> +static const struct xattr_handler
> +shiftfs_posix_acl_default_xattr_handler = {
> + .name = XATTR_NAME_POSIX_ACL_DEFAULT,
> + .flags = ACL_TYPE_DEFAULT,
> + .get = shiftfs_posix_acl_xattr_get,
> + .set = shiftfs_posix_acl_xattr_set,
> };
>
> -static int shiftfs_fill_super(struct super_block *sb, void *raw_data,
> - int silent)
> -{
> - struct shiftfs_data *data = raw_data;
> - char *name = kstrdup(data->path, GFP_KERNEL);
> - int err = -ENOMEM;
> - struct shiftfs_super_info *ssi = NULL;
> - struct path path;
> - struct dentry *dentry;
> +#else /* !CONFIG_SHIFT_FS_POSIX_ACL */
>
> - if (!name)
> - goto out;
> +#define shiftfs_get_acl NULL
>
> - ssi = kzalloc(sizeof(*ssi), GFP_KERNEL);
> - if (!ssi)
> - goto out;
> +#endif /* CONFIG_SHIFT_FS_POSIX_ACL */
>
> - err = -EPERM;
> - err = shiftfs_parse_options(ssi, data->data);
> +static const struct inode_operations shiftfs_dir_inode_operations = {
> + .lookup = shiftfs_lookup,
> + .mkdir = shiftfs_mkdir,
> + .symlink = shiftfs_symlink,
> + .unlink = shiftfs_unlink,
> + .rmdir = shiftfs_rmdir,
> + .rename = shiftfs_rename,
> + .link = shiftfs_link,
> + .setattr = shiftfs_setattr,
> + .create = shiftfs_create,
> + .mknod = shiftfs_mknod,
> + .permission = shiftfs_permission,
> + .getattr = shiftfs_getattr,
> + .listxattr = shiftfs_listxattr,
> + .get_acl = shiftfs_get_acl,
> +};
> +
> +static const struct inode_operations shiftfs_file_inode_operations = {
> + .fiemap = shiftfs_fiemap,
> + .getattr = shiftfs_getattr,
> + .get_acl = shiftfs_get_acl,
> + .listxattr = shiftfs_listxattr,
> + .permission = shiftfs_permission,
> + .setattr = shiftfs_setattr,
> + .tmpfile = shiftfs_tmpfile,
> +};
> +
> +static const struct inode_operations shiftfs_special_inode_operations = {
> + .getattr = shiftfs_getattr,
> + .get_acl = shiftfs_get_acl,
> + .listxattr = shiftfs_listxattr,
> + .permission = shiftfs_permission,
> + .setattr = shiftfs_setattr,
> +};
> +
> +static const struct inode_operations shiftfs_symlink_inode_operations = {
> + .getattr = shiftfs_getattr,
> + .get_link = shiftfs_get_link,
> + .listxattr = shiftfs_listxattr,
> + .setattr = shiftfs_setattr,
> +};
> +
> +static struct file *shiftfs_open_realfile(const struct file *file,
> + struct path *realpath)
> +{
> + struct file *lowerf;
> + const struct cred *oldcred;
> + struct inode *inode = file_inode(file);
> + struct inode *loweri = realpath->dentry->d_inode;
> + struct shiftfs_super_info *info = inode->i_sb->s_fs_info;
> +
> + oldcred = shiftfs_override_creds(inode->i_sb);
> + /* XXX: open_with_fake_path() not gauranteed to stay around, if
> + * removed use dentry_open() */
> + lowerf = open_with_fake_path(realpath, file->f_flags, loweri, info->creator_cred);
> + revert_creds(oldcred);
> +
> + return lowerf;
> +}
> +
> +#define SHIFTFS_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)
> +
> +static int shiftfs_change_flags(struct file *file, unsigned int flags)
> +{
> + struct inode *inode = file_inode(file);
> + int err;
> +
> + /* if some flag changed that cannot be changed then something's amiss */
> + if (WARN_ON((file->f_flags ^ flags) & ~SHIFTFS_SETFL_MASK))
> + return -EIO;
> +
> + flags &= SHIFTFS_SETFL_MASK;
> +
> + if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
> + return -EPERM;
> +
> + if (flags & O_DIRECT) {
> + if (!file->f_mapping->a_ops ||
> + !file->f_mapping->a_ops->direct_IO)
> + return -EINVAL;
> + }
> +
> + if (file->f_op->check_flags) {
> + err = file->f_op->check_flags(flags);
> + if (err)
> + return err;
> + }
> +
> + spin_lock(&file->f_lock);
> + file->f_flags = (file->f_flags & ~SHIFTFS_SETFL_MASK) | flags;
> + spin_unlock(&file->f_lock);
> +
> + return 0;
> +}
> +
> +static int shiftfs_real_fdget(const struct file *file, struct fd *lowerfd)
> +{
> + struct shiftfs_file_info *file_info = file->private_data;
> + struct file *realfile = file_info->realfile;
> +
> + lowerfd->flags = 0;
> + lowerfd->file = realfile;
> +
> + /* Did the flags change since open? */
> + if (unlikely(file->f_flags & lowerfd->file->f_flags))
> + return shiftfs_change_flags(lowerfd->file, file->f_flags);
> +
> + return 0;
> +}
> +
> +static int shiftfs_open(struct inode *inode, struct file *file)
> +{
> + struct shiftfs_super_info *ssi = inode->i_sb->s_fs_info;
> + struct shiftfs_file_info *file_info;
> + struct file *realfile;
> + struct path *realpath;
> +
> + file_info = kmem_cache_zalloc(shiftfs_file_info_cache, GFP_KERNEL);
> + if (!file_info)
> + return -ENOMEM;
> + file->private_data = file_info;
> +
> + realpath = &file_info->realpath;
> + realpath->mnt = ssi->mnt;
> + realpath->dentry = file->f_path.dentry->d_fsdata;
> +
> + realfile = shiftfs_open_realfile(file, realpath);
> + if (IS_ERR(realfile)) {
> + kfree(file_info);
> + return PTR_ERR(realfile);
> + }
> +
> + file_info->realfile = realfile;
> + return 0;
> +}
> +
> +static int shiftfs_release(struct inode *inode, struct file *file)
> +{
> + struct shiftfs_file_info *file_info = file->private_data;
> +
> + fput(file_info->realfile);
> + kmem_cache_free(shiftfs_file_info_cache, file_info);
> + return 0;
> +}
> +
> +static loff_t shiftfs_llseek(struct file *file, loff_t offset, int whence)
> +{
> + struct inode *realinode = file_inode(file)->i_private;
> +
> + return generic_file_llseek_size(file, offset, whence,
> + realinode->i_sb->s_maxbytes,
> + i_size_read(realinode));
> +}
> +
> +/* XXX: Need to figure out what to to about atime updates, maybe other
> + * timestamps too ... ref. ovl_file_accessed() */
> +
> +static rwf_t shiftfs_iocb_to_rwf(struct kiocb *iocb)
> +{
> + int ifl = iocb->ki_flags;
> + rwf_t flags = 0;
> +
> + if (ifl & IOCB_NOWAIT)
> + flags |= RWF_NOWAIT;
> + if (ifl & IOCB_HIPRI)
> + flags |= RWF_HIPRI;
> + if (ifl & IOCB_DSYNC)
> + flags |= RWF_DSYNC;
> + if (ifl & IOCB_SYNC)
> + flags |= RWF_SYNC;
> +
> + return flags;
> +}
> +
> +static ssize_t shiftfs_read_iter(struct kiocb *iocb, struct iov_iter *iter)
> +{
> + struct file *file = iocb->ki_filp;
> + struct fd lowerfd;
> + const struct cred *oldcred;
> + ssize_t ret;
> +
> + if (!iov_iter_count(iter))
> + return 0;
> +
> + ret = shiftfs_real_fdget(file, &lowerfd);
> + if (ret)
> + return ret;
> +
> + oldcred = shiftfs_override_creds(file->f_path.dentry->d_sb);
> + ret = vfs_iter_read(lowerfd.file, iter, &iocb->ki_pos,
> + shiftfs_iocb_to_rwf(iocb));
> + revert_creds(oldcred);
> +
> + shiftfs_file_accessed(file);
> +
> + fdput(lowerfd);
> + return ret;
> +}
> +
> +static ssize_t shiftfs_write_iter(struct kiocb *iocb, struct iov_iter *iter)
> +{
> + struct file *file = iocb->ki_filp;
> + struct inode *inode = file_inode(file);
> + struct fd lowerfd;
> + const struct cred *oldcred;
> + ssize_t ret;
> +
> + if (!iov_iter_count(iter))
> + return 0;
> +
> + inode_lock(inode);
> + /* Update mode */
> + shiftfs_copyattr(inode->i_private, inode);
> + ret = file_remove_privs(file);
> + if (ret)
> + goto out_unlock;
> +
> + ret = shiftfs_real_fdget(file, &lowerfd);
> + if (ret)
> + goto out_unlock;
> +
> + oldcred = shiftfs_override_creds(file->f_path.dentry->d_sb);
> + file_start_write(lowerfd.file);
> + ret = vfs_iter_write(lowerfd.file, iter, &iocb->ki_pos,
> + shiftfs_iocb_to_rwf(iocb));
> + file_end_write(lowerfd.file);
> + revert_creds(oldcred);
> +
> + /* Update size */
> + shiftfs_copyattr(inode->i_private, inode);
> +
> + fdput(lowerfd);
> +
> +out_unlock:
> + inode_unlock(inode);
> + return ret;
> +}
> +
> +static int shiftfs_fsync(struct file *file, loff_t start, loff_t end,
> + int datasync)
> +{
> + struct fd lowerfd;
> + const struct cred *oldcred;
> + int ret;
> +
> + ret = shiftfs_real_fdget(file, &lowerfd);
> + if (ret)
> + return ret;
> +
> + oldcred = shiftfs_override_creds(file->f_path.dentry->d_sb);
> + ret = vfs_fsync_range(lowerfd.file, start, end, datasync);
> + revert_creds(oldcred);
> +
> + fdput(lowerfd);
> + return ret;
> +}
> +
> +static int shiftfs_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> + struct shiftfs_file_info *file_info = file->private_data;
> + struct file *realfile = file_info->realfile;
> + const struct cred *oldcred;
> + int ret;
> +
> + if (!realfile->f_op->mmap)
> + return -ENODEV;
> +
> + if (WARN_ON(file != vma->vm_file))
> + return -EIO;
> +
> + oldcred = shiftfs_override_creds(file->f_path.dentry->d_sb);
> + vma->vm_file = get_file(realfile);
> + ret = call_mmap(vma->vm_file, vma);
> + revert_creds(oldcred);
> +
> + shiftfs_file_accessed(file);
> +
> + if (ret)
> + fput(realfile); /* Drop refcount from new vm_file value */
> + else
> + fput(file); /* Drop refcount from previous vm_file value */
> +
> + return ret;
> +}
> +
> +static long shiftfs_fallocate(struct file *file, int mode, loff_t offset,
> + loff_t len)
> +{
> + struct inode *inode = file_inode(file);
> + struct inode *loweri = inode->i_private;
> + struct fd lowerfd;
> + const struct cred *oldcred;
> + int ret;
> +
> + ret = shiftfs_real_fdget(file, &lowerfd);
> + if (ret)
> + return ret;
> +
> + oldcred = shiftfs_override_creds(file->f_path.dentry->d_sb);
> + ret = vfs_fallocate(lowerfd.file, mode, offset, len);
> + revert_creds(oldcred);
> +
> + /* Update size */
> + shiftfs_copyattr(loweri, inode);
> +
> + fdput(lowerfd);
> + return ret;
> +}
> +
> +static int shiftfs_fadvise(struct file *file, loff_t offset, loff_t len,
> + int advice)
> +{
> + struct fd lowerfd;
> + const struct cred *oldcred;
> + int ret;
> +
> + ret = shiftfs_real_fdget(file, &lowerfd);
> + if (ret)
> + return ret;
> +
> + oldcred = shiftfs_override_creds(file->f_path.dentry->d_sb);
> + ret = vfs_fadvise(lowerfd.file, offset, len, advice);
> + revert_creds(oldcred);
> +
> + fdput(lowerfd);
> + return ret;
> +}
> +
> +static int shiftfs_override_ioctl_creds(const struct super_block *sb,
> + const struct cred **oldcred,
> + struct cred **newcred)
> +{
> + kuid_t fsuid = current_fsuid();
> + kgid_t fsgid = current_fsgid();
> +
> + *oldcred = shiftfs_override_creds(sb);
> +
> + *newcred = prepare_creds();
> + if (!*newcred) {
> + revert_creds(*oldcred);
> + return -ENOMEM;
> + }
> +
> + (*newcred)->fsuid = KUIDT_INIT(from_kuid(sb->s_user_ns, fsuid));
> + (*newcred)->fsgid = KGIDT_INIT(from_kgid(sb->s_user_ns, fsgid));
> +
> + /* clear all caps to prevent bypassing capable() checks */
> + cap_clear((*newcred)->cap_bset);
> + cap_clear((*newcred)->cap_effective);
> + cap_clear((*newcred)->cap_inheritable);
> + cap_clear((*newcred)->cap_permitted);
> +
> + put_cred(override_creds(*newcred));
> + return 0;
> +}
> +
> +static inline void shiftfs_revert_ioctl_creds(const struct cred *oldcred,
> + struct cred *newcred)
> +{
> + return shiftfs_revert_object_creds(oldcred, newcred);
> +}
> +
> +static long shiftfs_real_ioctl(struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + long ret = 0;
> + struct fd lowerfd;
> + struct cred *newcred;
> + const struct cred *oldcred;
> + struct super_block *sb = file->f_path.dentry->d_sb;
> +
> + ret = shiftfs_real_fdget(file, &lowerfd);
> + if (ret)
> + return ret;
> +
> + ret = shiftfs_override_ioctl_creds(sb, &oldcred, &newcred);
> + if (ret)
> + goto out_fdput;
> +
> + ret = vfs_ioctl(lowerfd.file, cmd, arg);
> +
> + shiftfs_revert_ioctl_creds(oldcred, newcred);
> +
> + shiftfs_copyattr(file_inode(lowerfd.file), file_inode(file));
> + shiftfs_copyflags(file_inode(lowerfd.file), file_inode(file));
> +
> +out_fdput:
> + fdput(lowerfd);
> +
> + return ret;
> +}
> +
> +static long shiftfs_ioctl(struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + switch (cmd) {
> + case FS_IOC_GETVERSION:
> + /* fall through */
> + case FS_IOC_GETFLAGS:
> + /* fall through */
> + case FS_IOC_SETFLAGS:
> + break;
> + default:
> + return -ENOTTY;
> + }
> +
> + return shiftfs_real_ioctl(file, cmd, arg);
> +}
> +
> +static long shiftfs_compat_ioctl(struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + switch (cmd) {
> + case FS_IOC32_GETVERSION:
> + /* fall through */
> + case FS_IOC32_GETFLAGS:
> + /* fall through */
> + case FS_IOC32_SETFLAGS:
> + break;
> + default:
> + return -ENOIOCTLCMD;
> + }
> +
> + return shiftfs_real_ioctl(file, cmd, arg);
> +}
> +
> +enum shiftfs_copyop {
> + SHIFTFS_COPY,
> + SHIFTFS_CLONE,
> + SHIFTFS_DEDUPE,
> +};
> +
> +static ssize_t shiftfs_copyfile(struct file *file_in, loff_t pos_in,
> + struct file *file_out, loff_t pos_out, u64 len,
> + unsigned int flags, enum shiftfs_copyop op)
> +{
> + ssize_t ret;
> + struct fd real_in, real_out;
> + const struct cred *oldcred;
> + struct inode *inode_out = file_inode(file_out);
> + struct inode *loweri = inode_out->i_private;
> +
> + ret = shiftfs_real_fdget(file_out, &real_out);
> + if (ret)
> + return ret;
> +
> + ret = shiftfs_real_fdget(file_in, &real_in);
> + if (ret) {
> + fdput(real_out);
> + return ret;
> + }
> +
> + oldcred = shiftfs_override_creds(inode_out->i_sb);
> + switch (op) {
> + case SHIFTFS_COPY:
> + ret = vfs_copy_file_range(real_in.file, pos_in, real_out.file,
> + pos_out, len, flags);
> + break;
> +
> + case SHIFTFS_CLONE:
> + ret = vfs_clone_file_range(real_in.file, pos_in, real_out.file,
> + pos_out, len, flags);
> + break;
> +
> + case SHIFTFS_DEDUPE:
> + ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
> + real_out.file, pos_out, len,
> + flags);
> + break;
> + }
> + revert_creds(oldcred);
> +
> + /* Update size */
> + shiftfs_copyattr(loweri, inode_out);
> +
> + fdput(real_in);
> + fdput(real_out);
> +
> + return ret;
> +}
> +
> +static ssize_t shiftfs_copy_file_range(struct file *file_in, loff_t pos_in,
> + struct file *file_out, loff_t pos_out,
> + size_t len, unsigned int flags)
> +{
> + return shiftfs_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
> + SHIFTFS_COPY);
> +}
> +
> +static loff_t shiftfs_remap_file_range(struct file *file_in, loff_t pos_in,
> + struct file *file_out, loff_t pos_out,
> + loff_t len, unsigned int remap_flags)
> +{
> + enum shiftfs_copyop op;
> +
> + if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
> + return -EINVAL;
> +
> + if (remap_flags & REMAP_FILE_DEDUP)
> + op = SHIFTFS_DEDUPE;
> + else
> + op = SHIFTFS_CLONE;
> +
> + return shiftfs_copyfile(file_in, pos_in, file_out, pos_out, len,
> + remap_flags, op);
> +}
> +
> +static int shiftfs_iterate_shared(struct file *file, struct dir_context *ctx)
> +{
> + const struct cred *oldcred;
> + int err = -ENOTDIR;
> + struct shiftfs_file_info *file_info = file->private_data;
> + struct file *realfile = file_info->realfile;
> +
> + oldcred = shiftfs_override_creds(file->f_path.dentry->d_sb);
> + err = iterate_dir(realfile, ctx);
> + revert_creds(oldcred);
> +
> + return err;
> +}
> +
> +const struct file_operations shiftfs_file_operations = {
> + .open = shiftfs_open,
> + .release = shiftfs_release,
> + .llseek = shiftfs_llseek,
> + .read_iter = shiftfs_read_iter,
> + .write_iter = shiftfs_write_iter,
> + .fsync = shiftfs_fsync,
> + .mmap = shiftfs_mmap,
> + .fallocate = shiftfs_fallocate,
> + .fadvise = shiftfs_fadvise,
> + .unlocked_ioctl = shiftfs_ioctl,
> + .compat_ioctl = shiftfs_compat_ioctl,
> + .copy_file_range = shiftfs_copy_file_range,
> + .remap_file_range = shiftfs_remap_file_range,
> +};
> +
> +const struct file_operations shiftfs_dir_operations = {
> + .compat_ioctl = shiftfs_compat_ioctl,
> + .fsync = shiftfs_fsync,
> + .iterate_shared = shiftfs_iterate_shared,
> + .llseek = shiftfs_llseek,
> + .open = shiftfs_open,
> + .read = generic_read_dir,
> + .release = shiftfs_release,
> + .unlocked_ioctl = shiftfs_ioctl,
> +};
> +
> +static const struct address_space_operations shiftfs_aops = {
> + /* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
> + .direct_IO = noop_direct_IO,
> +};
> +
> +static void shiftfs_fill_inode(struct inode *inode, unsigned long ino,
> + umode_t mode, dev_t dev, struct dentry *dentry)
> +{
> + struct inode *loweri;
> +
> + inode->i_ino = ino;
> + inode->i_flags |= S_NOCMTIME;
> +
> + mode &= S_IFMT;
> + inode->i_mode = mode;
> + switch (mode & S_IFMT) {
> + case S_IFDIR:
> + inode->i_op = &shiftfs_dir_inode_operations;
> + inode->i_fop = &shiftfs_dir_operations;
> + break;
> + case S_IFLNK:
> + inode->i_op = &shiftfs_symlink_inode_operations;
> + break;
> + case S_IFREG:
> + inode->i_op = &shiftfs_file_inode_operations;
> + inode->i_fop = &shiftfs_file_operations;
> + inode->i_mapping->a_ops = &shiftfs_aops;
> + break;
> + default:
> + inode->i_op = &shiftfs_special_inode_operations;
> + init_special_inode(inode, mode, dev);
> + break;
> + }
> +
> + if (!dentry)
> + return;
> +
> + loweri = dentry->d_inode;
> + if (!loweri->i_op->get_link)
> + inode->i_opflags |= IOP_NOFOLLOW;
> +
> + shiftfs_copyattr(loweri, inode);
> + shiftfs_copyflags(loweri, inode);
> + set_nlink(inode, loweri->i_nlink);
> +}
> +
> +static int shiftfs_show_options(struct seq_file *m, struct dentry *dentry)
> +{
> + struct super_block *sb = dentry->d_sb;
> + struct shiftfs_super_info *sbinfo = sb->s_fs_info;
> +
> + if (sbinfo->mark)
> + seq_show_option(m, "mark", NULL);
> +
> + if (sbinfo->passthrough)
> + seq_printf(m, ",passthrough=%u", sbinfo->passthrough);
> +
> + return 0;
> +}
> +
> +static int shiftfs_statfs(struct dentry *dentry, struct kstatfs *buf)
> +{
> + struct super_block *sb = dentry->d_sb;
> + struct shiftfs_super_info *sbinfo = sb->s_fs_info;
> + struct dentry *root = sb->s_root;
> + struct dentry *realroot = root->d_fsdata;
> + struct path realpath = { .mnt = sbinfo->mnt, .dentry = realroot };
> + int err;
> +
> + err = vfs_statfs(&realpath, buf);
> if (err)
> - goto out;
> + return err;
>
> - /* to mark a mount point, must be real root */
> - if (ssi->mark && !capable(CAP_SYS_ADMIN))
> - goto out;
> + if (!shiftfs_passthrough_statfs(sbinfo))
> + buf->f_type = sb->s_magic;
>
> - /* else to mount a mark, must be userns admin */
> - if (!ssi->mark && !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
> - goto out;
> + return 0;
> +}
>
> - err = kern_path(name, LOOKUP_FOLLOW, &path);
> +static void shiftfs_evict_inode(struct inode *inode)
> +{
> + struct inode *loweri = inode->i_private;
> +
> + clear_inode(inode);
> +
> + if (loweri)
> + iput(loweri);
> +}
> +
> +static void shiftfs_put_super(struct super_block *sb)
> +{
> + struct shiftfs_super_info *sbinfo = sb->s_fs_info;
> +
> + if (sbinfo) {
> + mntput(sbinfo->mnt);
> + put_cred(sbinfo->creator_cred);
> + kfree(sbinfo);
> + }
> +}
> +
> +static const struct xattr_handler shiftfs_xattr_handler = {
> + .prefix = "",
> + .get = shiftfs_xattr_get,
> + .set = shiftfs_xattr_set,
> +};
> +
> +const struct xattr_handler *shiftfs_xattr_handlers[] = {
> +#ifdef CONFIG_SHIFT_FS_POSIX_ACL
> + &shiftfs_posix_acl_access_xattr_handler,
> + &shiftfs_posix_acl_default_xattr_handler,
> +#endif
> + &shiftfs_xattr_handler,
> + NULL
> +};
> +
> +static inline bool passthrough_is_subset(int old_flags, int new_flags)
> +{
> + if ((new_flags & old_flags) != new_flags)
> + return false;
> +
> + return true;
> +}
> +
> +static int shiftfs_remount(struct super_block *sb, int *flags, char *data)
> +{
> + int err;
> + struct shiftfs_super_info new = {};
> + struct shiftfs_super_info *info = sb->s_fs_info;
> +
> + err = shiftfs_parse_mount_options(&new, data);
> if (err)
> - goto out;
> + return err;
> +
> + /* Mark mount option cannot be changed. */
> + if (info->mark || (info->mark != new.mark))
> + return -EPERM;
> +
> + if (info->passthrough != new.passthrough) {
> + /* Don't allow exceeding passthrough options of mark mount. */
> + if (!passthrough_is_subset(info->info_mark->passthrough,
> + info->passthrough))
> + return -EPERM;
> +
> + info->passthrough = new.passthrough;
> + }
> +
> + return 0;
> +}
> +
> +static const struct super_operations shiftfs_super_ops = {
> + .put_super = shiftfs_put_super,
> + .show_options = shiftfs_show_options,
> + .statfs = shiftfs_statfs,
> + .remount_fs = shiftfs_remount,
> + .evict_inode = shiftfs_evict_inode,
> +};
> +
> +struct shiftfs_data {
> + void *data;
> + const char *path;
> +};
> +
> +static int shiftfs_fill_super(struct super_block *sb, void *raw_data,
> + int silent)
> +{
> + int err;
> + struct path path = {};
> + struct shiftfs_super_info *sbinfo_mp;
> + char *name = NULL;
> + struct inode *inode = NULL;
> + struct dentry *dentry = NULL;
> + struct shiftfs_data *data = raw_data;
> + struct shiftfs_super_info *sbinfo = NULL;
> +
> + if (!data->path)
> + return -EINVAL;
>
> - err = -EPERM;
> + sb->s_fs_info = kzalloc(sizeof(*sbinfo), GFP_KERNEL);
> + if (!sb->s_fs_info)
> + return -ENOMEM;
> + sbinfo = sb->s_fs_info;
> +
> + err = shiftfs_parse_mount_options(sbinfo, data->data);
> + if (err)
> + return err;
> +
> + /* to mount a mark, must be userns admin */
> + if (!sbinfo->mark && !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + name = kstrdup(data->path, GFP_KERNEL);
> + if (!name)
> + return -ENOMEM;
> +
> + err = kern_path(name, LOOKUP_FOLLOW, &path);
> + if (err)
> + goto out_free_name;
>
> if (!S_ISDIR(path.dentry->d_inode->i_mode)) {
> err = -ENOTDIR;
> - goto out_put;
> + goto out_put_path;
> }
>
> - sb->s_stack_depth = path.dentry->d_sb->s_stack_depth + 1;
> - if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
> - printk(KERN_ERR "shiftfs: maximum stacking depth exceeded\n");
> - err = -EINVAL;
> - goto out_put;
> - }
> + if (sbinfo->mark) {
> + struct super_block *lower_sb = path.mnt->mnt_sb;
> +
> + /* to mark a mount point, must root wrt lower s_user_ns */
> + if (!ns_capable(lower_sb->s_user_ns, CAP_SYS_ADMIN)) {
> + err = -EPERM;
> + goto out_put_path;
> + }
>
> - if (ssi->mark) {
> /*
> * this part is visible unshifted, so make sure no
> * executables that could be used to give suid
> * privileges
> */
> sb->s_iflags = SB_I_NOEXEC;
> - ssi->mnt = path.mnt;
> - dentry = path.dentry;
> - } else {
> - struct shiftfs_super_info *mp_ssi;
>
> /*
> - * this leg executes if we're admin capable in
> - * the namespace, so be very careful
> + * Handle nesting of shiftfs mounts by referring this mark
> + * mount back to the original mark mount. This is more
> + * efficient and alleviates concerns about stack depth.
> */
> + if (lower_sb->s_magic == SHIFTFS_MAGIC) {
> + sbinfo_mp = lower_sb->s_fs_info;
> +
> + /* Doesn't make sense to mark a mark mount */
> + if (sbinfo_mp->mark) {
> + err = -EINVAL;
> + goto out_put_path;
> + }
> +
> + if (!passthrough_is_subset(sbinfo_mp->passthrough,
> + sbinfo->passthrough)) {
> + err = -EPERM;
> + goto out_put_path;
> + }
> +
> + sbinfo->mnt = mntget(sbinfo_mp->mnt);
> + dentry = dget(path.dentry->d_fsdata);
> + } else {
> + sbinfo->mnt = mntget(path.mnt);
> + dentry = dget(path.dentry);
> + }
> +
> + sbinfo->creator_cred = prepare_creds();
> + if (!sbinfo->creator_cred) {
> + err = -ENOMEM;
> + goto out_put_path;
> + }
> + } else {
> + /*
> + * This leg executes if we're admin capable in the namespace,
> + * so be very careful.
> + */
> + err = -EPERM;
> if (path.dentry->d_sb->s_magic != SHIFTFS_MAGIC)
> - goto out_put;
> - mp_ssi = path.dentry->d_sb->s_fs_info;
> - if (!mp_ssi->mark)
> - goto out_put;
> - ssi->mnt = mntget(mp_ssi->mnt);
> + goto out_put_path;
> +
> + sbinfo_mp = path.dentry->d_sb->s_fs_info;
> + if (!sbinfo_mp->mark)
> + goto out_put_path;
> +
> + if (!passthrough_is_subset(sbinfo_mp->passthrough,
> + sbinfo->passthrough))
> + goto out_put_path;
> +
> + sbinfo->mnt = mntget(sbinfo_mp->mnt);
> + sbinfo->creator_cred = get_cred(sbinfo_mp->creator_cred);
> dentry = dget(path.dentry->d_fsdata);
> - path_put(&path);
> + sbinfo->info_mark = sbinfo_mp;
> + }
> +
> + sb->s_stack_depth = dentry->d_sb->s_stack_depth + 1;
> + if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
> + printk(KERN_ERR "shiftfs: maximum stacking depth exceeded\n");
> + err = -EINVAL;
> + goto out_put_path;
> + }
> +
> + inode = new_inode(sb);
> + if (!inode) {
> + err = -ENOMEM;
> + goto out_put_path;
> }
> - ssi->userns = get_user_ns(dentry->d_sb->s_user_ns);
> - sb->s_fs_info = ssi;
> + shiftfs_fill_inode(inode, dentry->d_inode->i_ino, S_IFDIR, 0, dentry);
> +
> + ihold(dentry->d_inode);
> + inode->i_private = dentry->d_inode;
> +
> sb->s_magic = SHIFTFS_MAGIC;
> sb->s_op = &shiftfs_super_ops;
> sb->s_xattr = shiftfs_xattr_handlers;
> sb->s_d_op = &shiftfs_dentry_ops;
> - sb->s_root = d_make_root(shiftfs_new_inode(sb, S_IFDIR, dentry));
> + sb->s_flags |= SB_POSIXACL;
> + sb->s_root = d_make_root(inode);
> + if (!sb->s_root) {
> + err = -ENOMEM;
> + goto out_put_path;
> + }
> +
> sb->s_root->d_fsdata = dentry;
> + sbinfo->userns = get_user_ns(dentry->d_sb->s_user_ns);
> + shiftfs_copyattr(dentry->d_inode, sb->s_root->d_inode);
>
> - return 0;
> + dentry = NULL;
> + err = 0;
>
> - out_put:
> +out_put_path:
> path_put(&path);
> - out:
> +
> +out_free_name:
> kfree(name);
> - kfree(ssi);
> +
> + dput(dentry);
> +
> return err;
> }
>
> @@ -764,17 +1864,26 @@ static struct file_system_type shiftfs_type = {
>
> static int __init shiftfs_init(void)
> {
> + shiftfs_file_info_cache = kmem_cache_create(
> + "shiftfs_file_info_cache", sizeof(struct shiftfs_file_info), 0,
> + SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT | SLAB_MEM_SPREAD, NULL);
> + if (!shiftfs_file_info_cache)
> + return -ENOMEM;
> +
> return register_filesystem(&shiftfs_type);
> }
>
> static void __exit shiftfs_exit(void)
> {
> unregister_filesystem(&shiftfs_type);
> + kmem_cache_destroy(shiftfs_file_info_cache);
> }
>
> MODULE_ALIAS_FS("shiftfs");
> MODULE_AUTHOR("James Bottomley");
> -MODULE_DESCRIPTION("uid/gid shifting bind filesystem");
> +MODULE_AUTHOR("Seth Forshee <seth.forshee at canonical.com>");
> +MODULE_AUTHOR("Christian Brauner <christian.brauner at ubuntu.com>");
> +MODULE_DESCRIPTION("id shifting filesystem");
> MODULE_LICENSE("GPL v2");
> module_init(shiftfs_init)
> module_exit(shiftfs_exit)
> --
> 2.20.1
>
>
> --
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