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. Thanks. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- 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