From: Thomas Weißschuh linux@weissschuh.net
[ 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 linux@weissschuh.net Signed-off-by: Willy Tarreau w@1wt.eu Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 d119cbbbc256f..9890e86c26172 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)