lib: stackinit: hide never-taken branch from compiler

BugLink: https://bugs.launchpad.net/bugs/2102118

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@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

This commit is contained in:

Kees Cook

2025-03-12 22:51:00 +09:00

committed by

Stefan Bader

parent 60aa5977df

commit 42916ce138

1 changed files with 1 additions and 0 deletions

									
										lib/stackinit_kunit.c
									
		+1
		
												View File
												
				@@ -199,6 +199,7 @@ static noinline void test_ ## name (struct kunit *test)		\

				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);	\