linux-kernel - [PATCH RFC namespace] Fix uninitialized uflags in SYSCALL_DEFINE5(move

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Message-ID: <e85f9977-0719-4de8-952e-8ecdd741a9d4@paulmck-laptop>
Date: Wed, 26 Feb 2025 11:18:49 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	sfr@...b.auug.org.au, linux-next@...r.kernel.org
Subject: [PATCH RFC namespace] Fix uninitialized uflags in
 SYSCALL_DEFINE5(move_mount)

The next-20250226 release gets an uninitialized-variable warning from the
move_mount syscall in builds with clang 19.1.5.  This variable is in fact
assigned only if the MOVE_MOUNT_F_EMPTY_PATH flag is set, but is then
unconditionally passed to getname_maybe_null(), which unconditionally
references it.

This patch simply sets uflags to zero in the same manner as is done
for lflags, which makes rcutorture happy, but might or might not be a
proper patch.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Christian Brauner <brauner@...nel.org>
Cc: Jan Kara <jack@...e.cz>
Cc: <linux-fsdevel@...r.kernel.org>
Cc: <linux-kernel@...r.kernel.org>
---
 namespace.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index 663bacefddfa6..80505d533cd23 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4617,6 +4617,7 @@ SYSCALL_DEFINE5(move_mount,
 	if (flags & MOVE_MOUNT_BENEATH)		mflags |= MNT_TREE_BENEATH;
 
 	lflags = 0;
+	uflags = 0;
 	if (flags & MOVE_MOUNT_F_SYMLINKS)	lflags |= LOOKUP_FOLLOW;
 	if (flags & MOVE_MOUNT_F_AUTOMOUNTS)	lflags |= LOOKUP_AUTOMOUNT;
 	if (flags & MOVE_MOUNT_F_EMPTY_PATH)	uflags = AT_EMPTY_PATH;
@@ -4625,6 +4626,7 @@ SYSCALL_DEFINE5(move_mount,
 		return PTR_ERR(from_name);
 
 	lflags = 0;
+	uflags = 0;
 	if (flags & MOVE_MOUNT_T_SYMLINKS)	lflags |= LOOKUP_FOLLOW;
 	if (flags & MOVE_MOUNT_T_AUTOMOUNTS)	lflags |= LOOKUP_AUTOMOUNT;
 	if (flags & MOVE_MOUNT_T_EMPTY_PATH)	uflags = AT_EMPTY_PATH;