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

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

[Rochan Avlur]

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>
---
 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;
-- 
2.45.2

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

[Christian Brauner]

Hi Rochan,

> 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>

Seems generally fine to me,
Acked-by: Christian Brauner (Amutable) <braurg>

-- 

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

[Chao Yu]

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;

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

[Rochan Avlur]

Hi Chao,

> > 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 for pointing that out. I wasn't aware of Zhan's patch when I
submitted mine. Happy to defer to the earlier submission.

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

[Jaegeuk Kim]

On 07/30, Christian Brauner via Linux-f2fs-devel wrote:
> Hi Rochan,
> 
> > 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>
> 
> Seems generally fine to me,
> Acked-by: Christian Brauner (Amutable) <braurg>

Thanks, let me applied Acked-by: to the first submitted patch, which is same.

> 
> -- 
> 
> 
> 
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

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

[patchwork-bot+f2fs]

Hello:

This patch was applied to jaegeuk/f2fs.git (dev)
by Jaegeuk Kim <jaegeuk@kernel.org>:

On Thu, 16 Jul 2026 10:59:08 +0800 you wrote:
> f2fs_xattr_advise_set() calls inode_owner_or_capable() with &nop_mnt_idmap
> before allowing the "system.advise" xattr to be set, instead of the idmap
> that the VFS passes to the ->set() handler.
> 
> f2fs supports idmapped mounts, so on such a mount this checks the caller's
> fsuid against the unmapped on-disk owner rather than the mapped owner: the
> actual owner can be wrongly denied with -EPERM and an unrelated caller
> wrongly allowed.  Pass the handler's idmap instead.
> 
> [...]

Here is the summary with links:
  - [f2fs-dev] f2fs: use the mount idmap for the owner check in f2fs_xattr_advise_set()
    https://git.kernel.org/jaegeuk/f2fs/c/a54ffce4637a

You are awesome, thank you!
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Re: [f2fs-dev] [PATCH] f2fs: use the mount idmap for the owner check in f2fs_xattr_advise_set()

[patchwork-bot+f2fs]

Hello:

This patch was applied to jaegeuk/f2fs.git (dev)
by Jaegeuk Kim <jaegeuk@kernel.org>:

On Tue, 28 Jul 2026 21:16:56 -0700 you 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.
> 
> [...]

Here is the summary with links:
  - [f2fs-dev] f2fs: use the mount idmap for the owner check in f2fs_xattr_advise_set()
    https://git.kernel.org/jaegeuk/f2fs/c/a54ffce4637a

You are awesome, thank you!
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