linux-kernel - [PATCH] fs: namespace: fix uninitialized variable use

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Message-Id: <20250226081201.1876195-1-arnd@kernel.org>
Date: Wed, 26 Feb 2025 09:11:54 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
	Jan Kara <jack@...e.cz>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Jeff Layton <jlayton@...nel.org>,
	Miklos Szeredi <mszeredi@...hat.com>,
	Josef Bacik <josef@...icpanda.com>,
	"Seth Forshee (DigitalOcean)" <sforshee@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [PATCH] fs: namespace: fix uninitialized variable use

From: Arnd Bergmann <arnd@...db.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@...db.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