APPLIED: [SRU][K][PATCH] UBUNTU: [SAUCE] shiftfs: fix -EOVERFLOW inside the container

[Stefan Bader]

On 31.01.23 17:11, Alexander Mikhalitsyn wrote:
> BugLink: https://bugs.launchpad.net/bugs/1990849
> 
> We haven't supported idmapped layers with shiftfs and moreover, that makes
> no sense. Once lower fs support idmapped mounts when shiftfs is not needed.
> 
> Starting from linux-image-5.15.0-48-generic users started seeing EOVERFLOW
> errors from the userspace side on a trivial fs operations inside the containers.
> 
> This is caused by patches ("fs: tweak fsuidgid_has_mapping()"),
> ("fs: support mapped mounts of mapped filesystems"). These patches extends
> and enables idmapped mounts support in Ubuntu kernel, but the problem is
> that shiftfs was not properly ported.
> 
> See also:
> ("namei: prepare for idmapped mounts")
> https://lore.kernel.org/all/20210121131959.646623-15-christian.brauner@ubuntu.com/
> ("overlayfs: do not mount on top of idmapped mounts")
> https://lore.kernel.org/all/20210121131959.646623-29-christian.brauner@ubuntu.com/
> as a reference.
> 
> This patch should be appied on top of kinetic/master-next and based on the
> changes by Andrea Righi 4c934edc66 ("UBUNTU: SAUCE: shiftfs: always rely on init_user_ns")
> 
> This commit together with 4c934edc66 ("UBUNTU: SAUCE: shiftfs: always rely on init_user_ns")
> have to be ported to the jammy tree too.
> 
> Fixes: d347e71d2c0 ("UBUNTU: [SAUCE] shiftfs: support kernel 5.15")
> Reported-by: Thomas Parrott <thomas.parrott at canonical.com>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn at canonical.com>
> ---

Applied to kinetic:linux/master-next. Thanks.

-Stefan

>   fs/shiftfs.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/shiftfs.c b/fs/shiftfs.c
> index a5338dc6290c..c7e8b88915b1 100644
> --- a/fs/shiftfs.c
> +++ b/fs/shiftfs.c
> @@ -632,10 +632,10 @@ static int shiftfs_rename(struct user_namespace *ns,
>   	struct inode *loweri_dir_old = lowerd_dir_old->d_inode,
>   		     *loweri_dir_new = lowerd_dir_new->d_inode;
>   	struct renamedata rd = {
> -		.old_mnt_userns	= ns,
> +		.old_mnt_userns	= &init_user_ns,
>   		.old_dir	= loweri_dir_old,
>   		.old_dentry	= lowerd_old,
> -		.new_mnt_userns	= ns,
> +		.new_mnt_userns	= &init_user_ns,
>   		.new_dir	= loweri_dir_new,
>   		.new_dentry	= lowerd_new,
>   	};
> @@ -972,7 +972,7 @@ shiftfs_posix_acl_xattr_set(const struct xattr_handler *handler,
>   		return -EOPNOTSUPP;
>   	if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
>   		return value ? -EACCES : 0;
> -	if (!inode_owner_or_capable(ns, inode))
> +	if (!inode_owner_or_capable(&init_user_ns, inode))
>   		return -EPERM;
>   
>   	if (value) {
> @@ -2016,6 +2016,16 @@ static int shiftfs_fill_super(struct super_block *sb, void *raw_data,
>   		goto out_put_path;
>   	}
>   
> +	/*
> +	 * It makes no sense to handle idmapped layers from shiftfs.
> +	 * And we didn't support it properly anyway.
> +	 */
> +	if (is_idmapped_mnt(path.mnt)) {
> +		err = -EINVAL;
> +		pr_err("idmapped layers are currently not supported\n");
> +		goto out_put_path;
> +	}
> +
>   	sb->s_flags |= SB_POSIXACL;
>   
>   	if (sbinfo->mark) {

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