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. We can not handle 2000 0000 0000. We can support at most 0 .. 1000 0000 0000 and 5000 0000 0000 .. 6000 0000 0000, but at runtime we have to choose A and disable parts of both ranges. > > 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. > > -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>
