Cmnt: [SRU][J][PATCH 1/2] UBUNTU: SAUCE: Revert "UBUNTU: SAUCE: overlayfs: Skip permission checking for trusted.overlayfs.* xattrs"

[Masahiro Yamada]

On 4/1/26 03:26, Massimiliano Pellizzer wrote:
> This reverts commit 3fb38c98e060b327cb58373775dcc95ed52d1f22.
>
> The reverted commit bypasses vfs_setxattr() in ovl_do_setxattr() by
> calling __vfs_setxattr_noperm() directly. After After upstream commit

"After" is doubled.


> c914c0e27eb0 ("ovl: use wrappers to all vfs_*xattr() calls")
> was backported, this routed security.capability writes during copy-up
> through the unchecked path, bypassing cap_convert_nscap() and enabling
> CVE-2023-2640 and CVE-2023-32629.
>
> CVE-2023-2640
> CVE-2023-32629
> Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
> ---
>   fs/overlayfs/overlayfs.h | 15 ++-------------
>   fs/xattr.c               | 36 ++++++------------------------------
>   include/linux/xattr.h    |  1 -
>   3 files changed, 8 insertions(+), 44 deletions(-)
>
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index 585797e23b547..43b211cf437cc 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -211,12 +211,7 @@ static inline int ovl_do_setxattr(struct ovl_fs *ofs, struct dentry *dentry,
>   				  const char *name, const void *value,
>   				  size_t size, int flags)
>   {
> -	struct inode *inode = dentry->d_inode;
> -	int err;
> -
> -	inode_lock(inode);
> -	err = __vfs_setxattr_noperm(&init_user_ns, dentry, name, value, size, flags);
> -	inode_unlock(inode);
> +	int err = vfs_setxattr(&init_user_ns, dentry, name, value, size, flags);
>   
>   	pr_debug("setxattr(%pd2, \"%s\", \"%*pE\", %zu, %d) = %i\n",
>   		 dentry, name, min((int)size, 48), value, size, flags, err);
> @@ -233,13 +228,7 @@ static inline int ovl_setxattr(struct ovl_fs *ofs, struct dentry *dentry,
>   static inline int ovl_do_removexattr(struct ovl_fs *ofs, struct dentry *dentry,
>   				     const char *name)
>   {
> -	struct inode *inode = dentry->d_inode;
> -	int err;
> -
> -	inode_lock(inode);
> -	err = __vfs_removexattr_noperm(&init_user_ns, dentry, name);
> -	inode_unlock(inode);
> -
> +	int err = vfs_removexattr(&init_user_ns, dentry, name);
>   	pr_debug("removexattr(%pd2, \"%s\") = %i\n", dentry, name, err);
>   	return err;
>   }
> diff --git a/fs/xattr.c b/fs/xattr.c
> index bad89a9144cc7..030f93f3f9d0e 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -239,7 +239,6 @@ int __vfs_setxattr_noperm(struct user_namespace *mnt_userns,
>   
>   	return error;
>   }
> -EXPORT_SYMBOL_GPL(__vfs_setxattr_noperm);
>   
>   /**
>    * __vfs_setxattr_locked - set an extended attribute while holding the inode
> @@ -474,34 +473,6 @@ __vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
>   }
>   EXPORT_SYMBOL(__vfs_removexattr);
>   
> -/**
> - *  __vfs_removexattr_noperm - perform removexattr operation without
> - *  performing permission checks.
> - *
> - *  @dentry - object to perform setxattr on
> - *  @name - xattr name to set
> - *
> - *  returns the result of the internal setxattr or setsecurity operations.
> - *
> - *  This function requires the caller to lock the inode's i_mutex before it
> - *  is executed. It also assumes that the caller will make the appropriate
> - *  permission checks.
> - */
> -int
> -__vfs_removexattr_noperm(struct user_namespace *mnt_userns,
> -			 struct dentry *dentry, const char *name)
> -{
> -	int error;
> -
> -	error =__vfs_removexattr(mnt_userns, dentry, name);
> -	if (!error) {
> -		fsnotify_xattr(dentry);
> -		evm_inode_post_removexattr(dentry, name);
> -	}
> -	return error;
> -}
> -EXPORT_SYMBOL_GPL(__vfs_removexattr_noperm);
> -
>   /**
>    * __vfs_removexattr_locked - set an extended attribute while holding the inode
>    * lock
> @@ -532,7 +503,12 @@ __vfs_removexattr_locked(struct user_namespace *mnt_userns,
>   	if (error)
>   		goto out;
>   
> -	error = __vfs_removexattr_noperm(mnt_userns, dentry, name);
> +	error = __vfs_removexattr(mnt_userns, dentry, name);
> +
> +	if (!error) {
> +		fsnotify_xattr(dentry);
> +		evm_inode_post_removexattr(dentry, name);
> +	}
>   
>   out:
>   	return error;
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index 077b3844f2eeb..4c379d23ec6e7 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -63,7 +63,6 @@ int __vfs_setxattr_locked(struct user_namespace *, struct dentry *,
>   int vfs_setxattr(struct user_namespace *, struct dentry *, const char *,
>   		 const void *, size_t, int);
>   int __vfs_removexattr(struct user_namespace *, struct dentry *, const char *);
> -int __vfs_removexattr_noperm(struct user_namespace *, struct dentry *, const char *);
>   int __vfs_removexattr_locked(struct user_namespace *, struct dentry *,
>   			     const char *, struct inode **);
>   int vfs_removexattr(struct user_namespace *, struct dentry *, const char *);