6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kees Cook <kees@xxxxxxxxxx>
commit 5c3793604f91123bf49bc792ce697a0bef4c173c upstream.
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: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
lib/stackinit_kunit.c | 1 +
1 file changed, 1 insertion(+)
--- a/lib/stackinit_kunit.c
+++ b/lib/stackinit_kunit.c
@@ -212,6 +212,7 @@ static noinline void test_ ## name (stru
static noinline 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); \
