On Thu, Jul 7, 2022 at 12:13 PM Marco Elver <elver@xxxxxxxxxx> wrote: > > On Fri, 1 Jul 2022 at 16:23, Alexander Potapenko <glider@xxxxxxxxxx> wrote: > > > > Use hooks from instrumented.h to notify bug detection tools about > > usercopy events in get_user() and put_user_size(). > > > > It's still unclear how to instrument put_user(), which assumes that > > instrumentation code doesn't clobber RAX. > > do_put_user_call() has a comment about KASAN clobbering %ax, doesn't > this also apply to KMSAN? If not, could we have a <asm/instrumented.h> > that provides helpers to push registers on the stack and pop them back > on return? In fact, yes, it is rather simple to not clobber %ax. A more important aspect of instrumenting get_user()/put_user() is to always evaluate `x` and `ptr` only once, because sometimes these macros get called like `put_user(v, sp++)`. I might have confused the effects of evaluating sp++ twice with some register clobbering. > Also it seems the test robot complained about this patch. Will fix in v5. > > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > > --- > > Link: https://linux-review.googlesource.com/id/Ia9f12bfe5832623250e20f1859fdf5cc485a2fce > > --- > > arch/x86/include/asm/uaccess.h | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h > > index 913e593a3b45f..1a8b5a234474f 100644 > > --- a/arch/x86/include/asm/uaccess.h > > +++ b/arch/x86/include/asm/uaccess.h > > @@ -5,6 +5,7 @@ > > * User space memory access functions > > */ > > #include <linux/compiler.h> > > +#include <linux/instrumented.h> > > #include <linux/kasan-checks.h> > > #include <linux/string.h> > > #include <asm/asm.h> > > @@ -99,11 +100,13 @@ extern int __get_user_bad(void); > > int __ret_gu; \ > > register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX); \ > > __chk_user_ptr(ptr); \ > > + instrument_copy_from_user_before((void *)&(x), ptr, sizeof(*(ptr))); \ > > asm volatile("call __" #fn "_%P4" \ > > : "=a" (__ret_gu), "=r" (__val_gu), \ > > ASM_CALL_CONSTRAINT \ > > : "0" (ptr), "i" (sizeof(*(ptr)))); \ > > (x) = (__force __typeof__(*(ptr))) __val_gu; \ > > + instrument_copy_from_user_after((void *)&(x), ptr, sizeof(*(ptr)), 0); \ > > __builtin_expect(__ret_gu, 0); \ > > }) > > > > @@ -248,7 +251,9 @@ extern void __put_user_nocheck_8(void); > > > > #define __put_user_size(x, ptr, size, label) \ > > do { \ > > + __typeof__(*(ptr)) __pus_val = x; \ > > __chk_user_ptr(ptr); \ > > + instrument_copy_to_user(ptr, &(__pus_val), size); \ > > switch (size) { \ > > case 1: \ > > __put_user_goto(x, ptr, "b", "iq", label); \ > > @@ -286,6 +291,7 @@ do { \ > > #define __get_user_size(x, ptr, size, label) \ > > do { \ > > __chk_user_ptr(ptr); \ > > + instrument_copy_from_user_before((void *)&(x), ptr, size); \ > > switch (size) { \ > > case 1: { \ > > unsigned char x_u8__; \ > > @@ -305,6 +311,7 @@ do { \ > > default: \ > > (x) = __get_user_bad(); \ > > } \ > > + instrument_copy_from_user_after((void *)&(x), ptr, size, 0); \ > > } while (0) > > > > #define __get_user_asm(x, addr, itype, ltype, label) \ > > -- > > 2.37.0.rc0.161.g10f37bed90-goog > > -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
