linux-kernel - [PATCH] x86/uaccess: instrument copy_from_user

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Message-ID: <20221025221755.3810809-1-glider@google.com>
Date:   Wed, 26 Oct 2022 00:17:55 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>, x86@...nel.org
Subject: [PATCH] x86/uaccess: instrument copy_from_user_nmi()

Make sure usercopy hooks from linux/instrumented.h are invoked for
copy_from_user_nmi().
This fixes KMSAN false positives reported when dumping opcodes for a
stack trace.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: x86@...nel.org
Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
 arch/x86/lib/usercopy.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index f1bb186171562..24b48af274173 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -6,6 +6,7 @@
 
 #include <linux/uaccess.h>
 #include <linux/export.h>
+#include <linux/instrumented.h>
 
 #include <asm/tlbflush.h>
 
@@ -44,7 +45,9 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
 	 * called from other contexts.
 	 */
 	pagefault_disable();
+	instrument_copy_from_user_before(to, from, n);
 	ret = raw_copy_from_user(to, from, n);
+	instrument_copy_from_user_after(to, from, n, ret);
 	pagefault_enable();
 
 	return ret;
-- 
2.38.0.135.g90850a2211-goog