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tools/nolibc: ensure stack protector guard is never zero

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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>
This commit is contained in:
Thomas Weißschuh 2023-05-21 11:36:31 +02:00 • committed by Paul E. McKenney
parent 7a9b234520
commit 88fc7eb54e
1 changed files with 3 additions and 2 deletions
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5
tools/include/nolibc/stackprotector.h
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@ -45,8 +45,9 @@ __attribute__((weak,no_stack_protector,section(".text.nolibc_stack_chk")))
void __stack_chk_init(void) void __stack_chk_init(void)
{ {
my_syscall3(__NR_getrandom, &__stack_chk_guard, sizeof(__stack_chk_guard), 0); my_syscall3(__NR_getrandom, &__stack_chk_guard, sizeof(__stack_chk_guard), 0);
/* a bit more randomness in case getrandom() fails */ /* a bit more randomness in case getrandom() fails, ensure the guard is never 0 */
__stack_chk_guard ^= (uintptr_t) &__stack_chk_guard; if (__stack_chk_guard != (uintptr_t) &__stack_chk_guard)
__stack_chk_guard ^= (uintptr_t) &__stack_chk_guard;
} }
#endif /* defined(NOLIBC_STACKPROTECTOR) */ #endif /* defined(NOLIBC_STACKPROTECTOR) */