From 047bbb3730c608f988e1e850fcd9ac5e26ad8346 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Date: Sun, 21 May 2023 11:36:31 +0200 Subject: [PATCH] tools/nolibc: ensure stack protector guard is never zero MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit [ Upstream commit 88fc7eb54ecc6db8b773341ce39ad201066fa7da ] The all-zero pattern is one of the more probable out-of-bound writes so add a special case to not accidentally accept it. Also it enables the reliable detection of stack protector initialization during testing. Signed-off-by: Thomas Weißschuh Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin --- tools/include/nolibc/stackprotector.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/tools/include/nolibc/stackprotector.h b/tools/include/nolibc/stackprotector.h index d119cbbbc256..9890e86c2617 100644 --- a/tools/include/nolibc/stackprotector.h +++ b/tools/include/nolibc/stackprotector.h @@ -45,8 +45,9 @@ __attribute__((weak,no_stack_protector,section(".text.nolibc_stack_chk"))) void __stack_chk_init(void) { my_syscall3(__NR_getrandom, &__stack_chk_guard, sizeof(__stack_chk_guard), 0); - /* a bit more randomness in case getrandom() fails */ - __stack_chk_guard ^= (uintptr_t) &__stack_chk_guard; + /* a bit more randomness in case getrandom() fails, ensure the guard is never 0 */ + if (__stack_chk_guard != (uintptr_t) &__stack_chk_guard) + __stack_chk_guard ^= (uintptr_t) &__stack_chk_guard; } #endif // defined(NOLIBC_STACKPROTECTOR)