On 03/26/2015 06:05 PM, Russell King - ARM Linux wrote: > On Fri, Mar 20, 2015 at 02:12:52PM +0300, Andrey Ryabinin wrote: >> Usually ELF_ET_DYN_BASE is 2/3 of TASK_SIZE. With 3G/1G user/kernel >> split this is not so, because 2*TASK_SIZE overflows 32 bits, >> so the actual value of ELF_ET_DYN_BASE is: >> (2 * TASK_SIZE / 3) = 0x2a000000 >> >> When ASLR is disabled PIE binaries will load at ELF_ET_DYN_BASE address. >> On 32bit platforms AddressSanitzer uses addresses [0x20000000 - 0x40000000] >> for shadow memory [1]. So ASan doesn't work for PIE binaries when ASLR disabled >> as it fails to map shadow memory. >> Also after Kees's 'split ET_DYN ASLR from mmap ASLR' patchset PIE binaries >> has a high chance of loading somewhere in between [0x2a000000 - 0x40000000] >> even if ASLR enabled. This makes ASan with PIE absolutely incompatible. >> >> Fix overflow by dividing TASK_SIZE prior to multiplying. >> After this patch ELF_ET_DYN_BASE equals to (for CONFIG_VMSPLIT_3G=y): >> (TASK_SIZE / 3 * 2) = 0x7f555554 >> >> [1] https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm#Mapping >> >> Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> >> Reported-by: Maria Guseva <m.guseva@xxxxxxxxxxx> >> Cc: stable@xxxxxxxxxxxxxxx > > Who's handling this patch? I'm guessing it should be me, so if it could > find its way into my patch system for when I next apply a bunch of patches, > that'd be good. > It's already there. Patch number - 8320/1. -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html