Re: [PATCH] f2fs: use the mount idmap for the owner check in f2fs_xattr_advise_set()

[Chao Yu <chao@kernel.org>]

On 7/29/26 12:16, Rochan Avlur wrote:
> f2fs_xattr_advise_set() calls inode_owner_or_capable() with
> &nop_mnt_idmap before allowing the advise xattr to be set, instead of
> the idmap that was passed into the handler.
> 
> Since f2fs supports idmapped mounts, this compares the caller's fsuid
> against the unmapped on-disk owner rather than the mapped owner; resulting
> in the actual owner to be wrongly denied with -EPERM. Use the idmap
> argument that was already passed to the xattr handler instead.
> 
> Fixes: 984fc4e76d63 ("f2fs: support idmapped mounts")
> Cc: stable@vger.kernel.org
> Signed-off-by: Rochan Avlur <rochan.avlur@gmail.com>

Thanks for the patch.

I notice there is already a patch:

https://lore.kernel.org/linux-f2fs-devel/20260716025908.608098-1-zhanxusheng@xiaomi.com

Thanks,

> ---
>   fs/f2fs/xattr.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
> index 610d5810074d..281e2fd6c778 100644
> --- a/fs/f2fs/xattr.c
> +++ b/fs/f2fs/xattr.c
> @@ -118,7 +118,7 @@ static int f2fs_xattr_advise_set(const struct xattr_handler *handler,
>   	unsigned char old_advise = F2FS_I(inode)->i_advise;
>   	unsigned char new_advise;
>   
> -	if (!inode_owner_or_capable(&nop_mnt_idmap, inode))
> +	if (!inode_owner_or_capable(idmap, inode))
>   		return -EPERM;
>   	if (value == NULL)
>   		return -EINVAL;