This is a note to let you know that I've just added the patch titled
lib: stackinit: hide never-taken branch from compiler
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
lib-stackinit-hide-never-taken-branch-from-compiler.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 26a524f5bd8f3ad36ca412ec745c9b541fc5aeae
Author: Kees Cook <kees@xxxxxxxxxx>
Date: Sun Nov 17 03:38:13 2024 -0800
lib: stackinit: hide never-taken branch from compiler
[ Upstream commit 5c3793604f91123bf49bc792ce697a0bef4c173c ]
The never-taken branch leads to an invalid bounds condition, which is by
design. To avoid the unwanted warning from the compiler, hide the
variable from the optimizer.
../lib/stackinit_kunit.c: In function 'do_nothing_u16_zero':
../lib/stackinit_kunit.c:51:49: error: array subscript 1 is outside array bounds of 'u16[0]' {aka 'short unsigned int[]'} [-Werror=array-bounds=]
51 | #define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
| ^~~~~~
../lib/stackinit_kunit.c:219:24: note: in expansion of macro 'DO_NOTHING_RETURN_SCALAR'
219 | return DO_NOTHING_RETURN_ ## which(ptr + 1); \
| ^~~~~~~~~~~~~~~~~~
Link: https://lkml.kernel.org/r/20241117113813.work.735-kees@xxxxxxxxxx
Signed-off-by: Kees Cook <kees@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/lib/test_stackinit.c b/lib/test_stackinit.c
index a3c74e6a21ff..56653c6a2a61 100644
--- a/lib/test_stackinit.c
+++ b/lib/test_stackinit.c
@@ -259,6 +259,7 @@ static noinline __init int test_ ## name (void) \
static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \
do_nothing_ ## name(var_type *ptr) \
{ \
+ OPTIMIZER_HIDE_VAR(ptr); \
/* Will always be true, but compiler doesn't know. */ \
if ((unsigned long)ptr > 0x2) \
return DO_NOTHING_RETURN_ ## which(ptr); \
