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Groups > linux.kernel > #1649730

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

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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 Daniel Micay's linux-hardened tree.

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 v2 0/5] stackprotector: ascii armor the stack canary riel@redhat.com - 2017-05-24 18:00 +0200
  [PATCH 1/5] random,stackprotect: introduce get_random_canary function riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 1/5] random,stackprotect: introduce get_random_canary function Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 3/5] x86: ascii armor the x86_64 boot init stack canary riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 3/5] x86: ascii armor the x86_64 boot init stack canary Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 2/5] fork,random: use get_random_canary to set tsk->stack_canary riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 2/5] fork,random: use get_random_canary to set tsk->stack_canary Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 5/5] sh64: ascii armor the sh64 boot init stack canary Rik van Riel <riel@redhat.com> - 2017-05-24 18:40 +0200
    Re: [PATCH 5/5] sh64: ascii armor the sh64 boot init stack canary Kees Cook <keescook@google.com> - 2017-05-24 18:40 +0200
  [PATCH 5/5] sh64: ascii armor the sh64 boot init stack canary riel@redhat.com - 2017-05-24 18:50 +0200

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