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Message-Id: <20170524155751.424-5-riel@redhat.com>
Date: Wed, 24 May 2017 11:57:50 -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 4/5] arm64: ascii armor the arm64 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/arm64/include/asm/stackprotector.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h
index fe5e287dc56b..b86a0865ddf1 100644
--- a/arch/arm64/include/asm/stackprotector.h
+++ b/arch/arm64/include/asm/stackprotector.h
@@ -30,6 +30,7 @@ static __always_inline void boot_init_stack_canary(void)
/* Try to get a semi random initial value. */
get_random_bytes(&canary, sizeof(canary));
canary ^= LINUX_VERSION_CODE;
+ canary &= CANARY_MASK;
current->stack_canary = canary;
__stack_chk_guard = current->stack_canary;
--
2.9.3
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