On Mon, Aug 7, 2017 at 12:03 PM, Kostya Serebryany <kcc@xxxxxxxxxx> wrote: > > > On Mon, Aug 7, 2017 at 11:57 AM, Kees Cook <keescook@xxxxxxxxxx> wrote: >> >> On Mon, Aug 7, 2017 at 11:51 AM, Evgenii Stepanov <eugenis@xxxxxxxxxx> >> wrote: >> > On Mon, Aug 7, 2017 at 11:40 AM, Kees Cook <keescook@xxxxxxxxxx> wrote: >> >> On Mon, Aug 7, 2017 at 11:36 AM, Evgenii Stepanov <eugenis@xxxxxxxxxx> >> >> wrote: >> >>> MSan is 64-bit only and does not allow any mappings _outside_ of these >> >>> regions: >> >>> 000000000000 - 010000000000 app-1 >> >>> 510000000000 - 600000000000 app-2 >> >>> 700000000000 - 800000000000 app-3 >> >>> >> >>> https://github.com/google/sanitizers/issues/579 >> >>> >> >>> It sounds like the ELF_ET_DYN_BASE change should not break MSan. >> >> >> >> Hah, so the proposed move to 0x1000 8000 0000 for ASan would break >> >> MSan. Lovely! :P >> > >> > That's unfortunate. >> > This will not help existing binaries, but going forward the mapping >> > can be adjusted at runtime to anything like >> > 000000000000 .. A >> > 500000000000 + A .. 600000000000 >> > 700000000000 .. 800000000000 >> > i.e. we can look at where the binary is mapped and set A to anything >> > in the range of [0, 1000 0000 0000). That's still not compatible with >> > 0x1000 8000 0000 though. >> >> So A is considered to be < 0x1000 0000 0000? And a future MSan could >> handle a PIE base of 0x2000 0000 0000? If ASan an TSan can handle that >> too, then we could use that as the future PIE base. Existing systems >> will need some sort of reversion. >> >> The primary concerns with the CVEs fixed with the PIE base commit was >> for 32-bit. While it is possible to collide on 64-bit, it is much more >> rare. As long as we have no problems with the new 32-bit PIE base, we >> can revert the 64-bit base default back to 0x5555 5555 4000. > > > Yes, please!! > > Also, would it be possible to introduce some kind of regression testing into > the kernel testing process to avoid such breakages in future? > It would be as simple as running a handful of commands like this (for gcc > and clang, for asan/tsan/msan, for 32-bit and 64-bit) > echo "int main(){}" | clang -x c++ - -fsanitize=address && ./a.out I was actually going to ask why the *San developers didn't notice the change? It lived in linux-next for months. :P Can you please add a test for what you need to the tools/testing/selftests/ tree? A gcc-based test would be preferred, of course. -Kees -- Kees Cook Pixel Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
