On Fri, Feb 10, 2023 at 12:35 AM Marco Elver <elver@xxxxxxxxxx> wrote: > > On Thu, 9 Feb 2023 at 23:43, Andrey Konovalov <andreyknvl@xxxxxxxxx> wrote: > > > > On Wed, Feb 8, 2023 at 7:42 PM Marco Elver <elver@xxxxxxxxxx> wrote: > > > > > > Clang 15 will provide an option to prefix calls to memcpy/memset/memmove > > > with __asan_ in instrumented functions: https://reviews.llvm.org/D122724 > > > > Hi Marco, > > > > Does this option affect all functions or only the ones that are marked > > with no_sanitize? > > Only functions that are instrumented, i.e. wherever > fsanitize=kernel-address inserts instrumentation. Ack. > > Based on the LLVM patch description, should we also change the normal > > memcpy/memset/memmove to be noninstrumented? > > They are no longer instrumented as of 69d4c0d32186 (for > CONFIG_GENERIC_ENTRY arches). Ah, sorry, overlooked that. > > These __asan_mem* functions are not defined in the kernel AFAICS. > > Should we add them? > > Peter introduced them in 69d4c0d32186, and we effectively have no > mem*() instrumentation on x86 w/o the compiler-enablement patch here. > > > Or maybe we should just use "__" as the prefix, as right now __mem* > > functions are the ones that are not instrumented? > > __asan_mem* is for instrumented code, just like ASan userspace does > (actually ASan userspace has been doing it like this forever, just the > kernel was somehow special). > > [...] > > > Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions") > > > Signed-off-by: Marco Elver <elver@xxxxxxxxxx> > > > --- > > > > > > The Fixes tag is just there to show the dependency, and that people > > > shouldn't apply this patch without 69d4c0d32186. > > ^^^ Depends on this commit, which is only in -tip. Got it. Missed that patch. > > > +ifdef CONFIG_GENERIC_ENTRY > > It also only affects GENERIC_ENTRY arches. > > > > +# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*() > > > +# instead. With compilers that don't support this option, compiler-inserted > > > +# memintrinsics won't be checked by KASAN. > > > +CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix) > > > +endif > > Probably the same should be done for SW_TAGS, because arm64 will be > GENERIC_ENTRY at one point or another as well. Yes, makes sense. I'll file a bug for this once I fully understand the consequences of these changes. > KASAN + GCC on x86 will have no mem*() instrumentation after > 69d4c0d32186, which is sad, so somebody ought to teach it the same > param as above. Hm, with that patch we would have no KASAN checking within normal mem* functions (not the ones embedded by the compiler) on GENERIC_ENTRY arches even with Clang, right?
