[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()

[Zhan Xusheng]

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.

Fixes: 01beba7957a2 ("fs: port inode_owner_or_capable() to mnt_idmap")
Cc: stable@vger.kernel.org
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.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 ed33e5110f2a..6728d1488cad 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -119,7 +119,7 @@ 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;
-- 
2.43.0

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

[Chao Yu]

On 7/16/26 10:59, Zhan Xusheng 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.
> 
> Fixes: 01beba7957a2 ("fs: port inode_owner_or_capable() to mnt_idmap")
> Cc: stable@vger.kernel.org
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,

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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