linux-kernel - [PATCH AUTOSEL 5.4 16/19] arm64: Mark __stack_chk_guard as __ro_after

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Date:   Wed, 22 Sep 2021 23:38:50 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dan Li <ashimida@...ux.alibaba.com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Sasha Levin <sashal@...nel.org>, will@...nel.org,
        peterz@...radead.org, maz@...nel.org, pcc@...gle.com,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.4 16/19] arm64: Mark __stack_chk_guard as __ro_after_init

From: Dan Li <ashimida@...ux.alibaba.com>

[ Upstream commit 9fcb2e93f41c07a400885325e7dbdfceba6efaec ]

__stack_chk_guard is setup once while init stage and never changed
after that.

Although the modification of this variable at runtime will usually
cause the kernel to crash (so does the attacker), it should be marked
as __ro_after_init, and it should not affect performance if it is
placed in the ro_after_init section.

Signed-off-by: Dan Li <ashimida@...ux.alibaba.com>
Acked-by: Mark Rutland <mark.rutland@....com>
Link: https://lore.kernel.org/r/1631612642-102881-1-git-send-email-ashimida@linux.alibaba.com
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kernel/process.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 7d7cfa128b71..f61ef46ebff7 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -56,7 +56,7 @@
 
 #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
 #include <linux/stackprotector.h>
-unsigned long __stack_chk_guard __read_mostly;
+unsigned long __stack_chk_guard __ro_after_init;
 EXPORT_SYMBOL(__stack_chk_guard);
 #endif
 
-- 
2.30.2