| From | "Paul E. McKenney" <> | Subject | [PATCH v2 nolibc 27/53] tools/nolibc: ensure stack protector guard is never zero | Date | Mon, 12 Jun 2023 13:44:48 -0700 |
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From: Thomas Weißschuh <linux@weissschuh.net>
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> --- 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 77e5251c4490..b0156fc077a0 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) */ -- 2.40.1
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