[PATCH] fs: fix incorrect lflags value in the move_mount syscall

[PATCH] fs: fix incorrect lflags value in the move_mount syscall

[Yuntao Wang]

The lflags value used to look up from_path was overwritten by the one used
to look up to_path.

In other words, from_path was looked up with the wrong lflags value. Fix it.

Fixes: f9fde814de37 ("fs: support getname_maybe_null() in move_mount()")
Signed-off-by: Yuntao Wang <yuntao.wang@linux.dev>
---
 fs/namespace.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index ddfd4457d338..43665cb6df28 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4551,20 +4551,13 @@ SYSCALL_DEFINE5(move_mount,
 	if (flags & MOVE_MOUNT_SET_GROUP)	mflags |= MNT_TREE_PROPAGATION;
 	if (flags & MOVE_MOUNT_BENEATH)		mflags |= MNT_TREE_BENEATH;
 
-	lflags = 0;
-	if (flags & MOVE_MOUNT_F_SYMLINKS)	lflags |= LOOKUP_FOLLOW;
-	if (flags & MOVE_MOUNT_F_AUTOMOUNTS)	lflags |= LOOKUP_AUTOMOUNT;
-	uflags = 0;
-	if (flags & MOVE_MOUNT_F_EMPTY_PATH)	uflags = AT_EMPTY_PATH;
-	from_name = getname_maybe_null(from_pathname, uflags);
-	if (IS_ERR(from_name))
-		return PTR_ERR(from_name);
-
 	lflags = 0;
 	if (flags & MOVE_MOUNT_T_SYMLINKS)	lflags |= LOOKUP_FOLLOW;
 	if (flags & MOVE_MOUNT_T_AUTOMOUNTS)	lflags |= LOOKUP_AUTOMOUNT;
+
 	uflags = 0;
 	if (flags & MOVE_MOUNT_T_EMPTY_PATH)	uflags = AT_EMPTY_PATH;
+
 	to_name = getname_maybe_null(to_pathname, uflags);
 	if (IS_ERR(to_name))
 		return PTR_ERR(to_name);
@@ -4582,6 +4575,17 @@ SYSCALL_DEFINE5(move_mount,
 			return ret;
 	}
 
+	lflags = 0;
+	if (flags & MOVE_MOUNT_F_SYMLINKS)	lflags |= LOOKUP_FOLLOW;
+	if (flags & MOVE_MOUNT_F_AUTOMOUNTS)	lflags |= LOOKUP_AUTOMOUNT;
+
+	uflags = 0;
+	if (flags & MOVE_MOUNT_F_EMPTY_PATH)	uflags = AT_EMPTY_PATH;
+
+	from_name = getname_maybe_null(from_pathname, uflags);
+	if (IS_ERR(from_name))
+		return PTR_ERR(from_name);
+
 	if (!from_name && from_dfd >= 0) {
 		CLASS(fd_raw, f_from)(from_dfd);
 		if (fd_empty(f_from))
-- 
2.50.1

Re: [PATCH] fs: fix incorrect lflags value in the move_mount syscall

[Christian Brauner]

On Mon, 11 Aug 2025 13:24:26 +0800, Yuntao Wang wrote:
> The lflags value used to look up from_path was overwritten by the one used
> to look up to_path.
> 
> In other words, from_path was looked up with the wrong lflags value. Fix it.
> 
> 

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] fs: fix incorrect lflags value in the move_mount syscall
      https://git.kernel.org/vfs/vfs/c/593d9e4c3d63

Re: [PATCH] fs: fix incorrect lflags value in the move_mount syscall

[Yuntao Wang]

On Mon, 11 Aug 2025 16:06:59 +0200, Christian Brauner <brauner@kernel.org> wrote:

> On Mon, 11 Aug 2025 13:24:26 +0800, Yuntao Wang wrote:
> > The lflags value used to look up from_path was overwritten by the one used
> > to look up to_path.
> > 
> > In other words, from_path was looked up with the wrong lflags value. Fix it.
> > 
> > 
> 
> Applied to the vfs.fixes branch of the vfs/vfs.git tree.
> Patches in the vfs.fixes branch should appear in linux-next soon.
> 
> Please report any outstanding bugs that were missed during review in a
> new review to the original patch series allowing us to drop it.
> 
> It's encouraged to provide Acked-bys and Reviewed-bys even though the
> patch has now been applied. If possible patch trailers will be updated.
> 
> Note that commit hashes shown below are subject to change due to rebase,
> trailer updates or similar. If in doubt, please check the listed branch.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
> branch: vfs.fixes
> 
> [1/1] fs: fix incorrect lflags value in the move_mount syscall
>       https://git.kernel.org/vfs/vfs/c/593d9e4c3d63

Hi Christian,

It seems the patch hasn't been applied to the vfs.fixes branch, the relevant
code there appears unchanged.

Thanks,
Yuntao

Re: [PATCH] fs: fix incorrect lflags value in the move_mount syscall

[Christian Brauner]

On Mon, Aug 11, 2025 at 01:24:26PM +0800, Yuntao Wang wrote:
> The lflags value used to look up from_path was overwritten by the one used
> to look up to_path.
> 
> In other words, from_path was looked up with the wrong lflags value. Fix it.

Right, thanks.