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!! For the revert, can you clarify which architectures this is a problem for? And confirm that the current 32-bit PIE base is not bugged? I'd like to minimize the revert. -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>
