[PATCH] fs: namespace: fix uninitialized variable use

[PATCH] fs: namespace: fix uninitialized variable use

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

clang correctly notices that the 'uflags' variable initialization
only happens in some cases:

fs/namespace.c:4622:6: error: variable 'uflags' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
 4622 |         if (flags & MOVE_MOUNT_F_EMPTY_PATH)    uflags = AT_EMPTY_PATH;
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fs/namespace.c:4623:48: note: uninitialized use occurs here
 4623 |         from_name = getname_maybe_null(from_pathname, uflags);
      |                                                       ^~~~~~
fs/namespace.c:4622:2: note: remove the 'if' if its condition is always true
 4622 |         if (flags & MOVE_MOUNT_F_EMPTY_PATH)    uflags = AT_EMPTY_PATH;
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: b1e9423d65e3 ("fs: support getname_maybe_null() in move_mount()")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 fs/namespace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index 663bacefddfa..7a531e03cb3c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4619,6 +4619,7 @@ SYSCALL_DEFINE5(move_mount,
 	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))
@@ -4627,6 +4628,7 @@ SYSCALL_DEFINE5(move_mount,
 	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))
-- 
2.39.5

Re: [PATCH] fs: namespace: fix uninitialized variable use

[Christian Brauner]

On Wed, 26 Feb 2025 09:11:54 +0100, Arnd Bergmann wrote:
> clang correctly notices that the 'uflags' variable initialization
> only happens in some cases:
> 
> fs/namespace.c:4622:6: error: variable 'uflags' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>  4622 |         if (flags & MOVE_MOUNT_F_EMPTY_PATH)    uflags = AT_EMPTY_PATH;
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> fs/namespace.c:4623:48: note: uninitialized use occurs here
>  4623 |         from_name = getname_maybe_null(from_pathname, uflags);
>       |                                                       ^~~~~~
> fs/namespace.c:4622:2: note: remove the 'if' if its condition is always true
>  4622 |         if (flags & MOVE_MOUNT_F_EMPTY_PATH)    uflags = AT_EMPTY_PATH;
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> [...]

Applied to the vfs-6.15.mount.namespace branch of the vfs/vfs.git tree.
Patches in the vfs-6.15.mount.namespace 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-6.15.mount.namespace

[1/1] fs: namespace: fix uninitialized variable use
      https://git.kernel.org/vfs/vfs/c/980512134163