On Wed, Oct 26, 2022 at 12:17:55AM +0200, 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 <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
> ---
> 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;
Is all that instrumentation NMI safe? ISTR having seen locks in some of
that *SAN stuff.
Also did this want:
Fixes: 59298997df89 ("x86/uaccess: avoid check_object_size() in copy_from_user_nmi()")
?
