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Date: Wed, 24 May 2017 11:57:49 -0400
From: riel@...hat.com
To: linux-kernel@...r.kernel.org
Cc: danielmicay@...il.com, tytso@....edu, keescook@...omium.org, hpa@...or.com,
luto@...capital.net, mingo@...nel.org, x86@...nel.org,
linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
linux-sh@...r.kernel.org, ysato@...rs.sourceforge.jp,
kernel-hardening@...ts.openwall.com
Subject: [PATCH 3/5] x86: ascii armor the x86_64 boot init stack canary
From: Rik van Riel <riel@...hat.com>
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 Daniel Micay's linux-hardened tree.
Signed-off-by: Rik van Riel <riel@...hat.com>
---
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
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