From mboxrd@z Thu Jan 1 00:00:00 1970 From: riel@redhat.com (riel at redhat.com) Date: Fri, 19 May 2017 17:26:34 -0400 Subject: [PATCH 3/5] x86: ascii armor the x86_64 boot init stack canary In-Reply-To: <20170519212636.30440-1-riel@redhat.com> References: <20170519212636.30440-1-riel@redhat.com> Message-ID: <20170519212636.30440-4-riel@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Rik van Riel Use the ascii-armor canary to prevent unterminated C string overflows from being able to successfully overwrite the canary, even if they somehow obtain the canary value. Inspired by execshield ascii-armor and PaX/grsecurity. Signed-off-by: Rik van Riel --- arch/x86/include/asm/stackprotector.h | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index dcbd9bcce714..8abedf1d650e 100644 --- a/arch/x86/include/asm/stackprotector.h +++ b/arch/x86/include/asm/stackprotector.h @@ -74,6 +74,7 @@ static __always_inline void boot_init_stack_canary(void) get_random_bytes(&canary, sizeof(canary)); tsc = rdtsc(); canary += tsc + (tsc << 32UL); + canary &= CANARY_MASK; current->stack_canary = canary; #ifdef CONFIG_X86_64 -- 2.9.3