On Tue, Feb 24, 2026 at 09:36:38AM +0100, Horst Birthelmer wrote:

On Mon, Feb 23, 2026 at 03:06:50PM -0800, Darrick J. Wong wrote:

quoted

From: Darrick J. Wong <djwong@kernel.org>

gcc 15 complains about an uninitialized variable val that is passed by
reference into fuse_conn_limit_write:

 control.c: In function ‘fuse_conn_congestion_threshold_write’:
 include/asm-generic/rwonce.h:55:37: warning: ‘val’ may be used uninitialized [-Wmaybe-uninitialized]
    55 |         *(volatile typeof(x) *)&(x) = (val);                            \
       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
 include/asm-generic/rwonce.h:61:9: note: in expansion of macro ‘__WRITE_ONCE’
    61 |         __WRITE_ONCE(x, val);                                           \
       |         ^~~~~~~~~~~~
 control.c:178:9: note: in expansion of macro ‘WRITE_ONCE’
   178 |         WRITE_ONCE(fc->congestion_threshold, val);
       |         ^~~~~~~~~~
 control.c:166:18: note: ‘val’ was declared here
   166 |         unsigned val;
       |                  ^~~

Unfortunately there's enough macro spew involved in kstrtoul_from_user
that I think gcc gives up on its analysis and sprays the above warning.
AFAICT it's not actually a bug, but we could just zero-initialize the
variable to enable using -Wmaybe-uninitialized to find real problems.

Previously we would use some weird uninitialized_var annotation to quiet
down the warnings, so clearly this code has been like this for quite
some time.

Cc: <redacted> # v5.9
Fixes: 3f649ab728cda8 ("treewide: Remove uninitialized_var() usage")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/fuse/control.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/control.c b/fs/fuse/control.c
index 140bd5730d9984..073c2d8e4dfc7c 100644
--- a/fs/fuse/control.c
+++ b/fs/fuse/control.c

@@ -121,7 +121,7 @@ static ssize_t fuse_conn_max_background_write(struct file *file,
 					      const char __user *buf,
 					      size_t count, loff_t *ppos)
 {
-	unsigned val;
+	unsigned val = 0;
 	ssize_t ret;
 
 	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,

@@ -163,7 +163,7 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
 						    const char __user *buf,
 						    size_t count, loff_t *ppos)
 {
-	unsigned val;
+	unsigned val = 0;
 	struct fuse_conn *fc;
 	ssize_t ret;
 

This looks good to me. Trivial fix for an annoying problem.
Reviewed-by: Horst Birthelmer <redacted>

Thanks for the review!

--D