linux-kernel - [PATCH] x86/mce/dev-mcelog: Fix potential memory access error

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Message-Id: <1617011360-102531-1-git-send-email-yang.lee@linux.alibaba.com>
Date:   Mon, 29 Mar 2021 17:49:20 +0800
From:   Yang Li <yang.lee@...ux.alibaba.com>
To:     tony.luck@...el.com
Cc:     bp@...en8.de, tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
        hpa@...or.com, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yang Li <yang.lee@...ux.alibaba.com>
Subject: [PATCH] x86/mce/dev-mcelog: Fix potential memory access error

Using set_bit() to set a bit in an integer is not a good idea, since
the function expects an unsigned long as argument, which can be 64bit
wide.
Coverity reports this problem as

High:Out-of-bounds access(INCOMPATIBLE_CAST)
CWE119: Out-of-bounds access to a scalar
Pointer "&mcelog->flags" points to an object whose effective type is
"unsigned int" (32 bits, unsigned) but is dereferenced as a wider
"unsigned long" (64 bits, unsigned). This may lead to memory corruption.

/home/heyuan.shy/git-repo/linux/arch/x86/kernel/cpu/mce/dev-mcelog.c:
dev_mce_log

Just use BIT instead.

Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@...ux.alibaba.com>
---
 arch/x86/kernel/cpu/mce/dev-mcelog.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mce/dev-mcelog.c b/arch/x86/kernel/cpu/mce/dev-mcelog.c
index 100fbee..fd7b1b4 100644
--- a/arch/x86/kernel/cpu/mce/dev-mcelog.c
+++ b/arch/x86/kernel/cpu/mce/dev-mcelog.c
@@ -51,7 +51,7 @@ static int dev_mce_log(struct notifier_block *nb, unsigned long val,
 	 * earlier errors are the more interesting ones:
 	 */
 	if (entry >= mcelog->len) {
-		set_bit(MCE_OVERFLOW, (unsigned long *)&mcelog->flags);
+		mcelog->flags |= BIT(MCE_OVERFLOW);
 		goto unlock;
 	}
 
-- 
1.8.3.1