[PATCH 2/5] x86/uaccess: instrument copy_from_user_nmi()

Alexander Potapenko
2022-11-02T11:06:24Z

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@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: x86@kernel.org
Signed-off-by: Alexander Potapenko <glider@google.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;
--
2.38.1.273.g43a17bfeac-goog