2022-11-02 11:26:36

by Alexander Potapenko

Subject: [PATCH 2/5] 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 <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: [email protected]
Signed-off-by: Alexander Potapenko <[email protected]>
---
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

2022-11-02 13:39:57

by Peter Zijlstra

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

On Wed, Nov 02, 2022 at 12:06:08PM +0100, Alexander Potapenko wrote:
> 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 <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Peter Zijlstra (Intel) <[email protected]>
> Cc: [email protected]
> Signed-off-by: Alexander Potapenko <[email protected]>

Acked-by: Peter Zijlstra (Intel) <[email protected]>

> ---
> 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
>