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[PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary

From riel@redhat.com
Newsgroups linux.kernel
Subject [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary
Date 2017-05-19 23:40 +0200
Message-ID <tIXMR-86v-15@gated-at.bofh.it> (permalink)
References <tIXMR-86v-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: Rik van Riel <riel@redhat.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 PaX/grsecurity.

Signed-off-by: Rik van Riel <riel@redhat.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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[PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary riel@redhat.com - 2017-05-19 23:40 +0200

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