UPSTREAM: ARM: 8320/1: fix integer overflow in ELF_ET_DYN_BASE
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
BUG=chromium:737531
TEST=Build and run
Change-Id: I06e157de83517c23ddfc92ad14d007f2ded9c39f
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Reported-by: Maria Guseva <m.guseva@samsung.com>
Cc: stable@vger.kernel.org
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Guenter Roeck <groeck@chromium.org>
(cherry picked from commit 8defb3367fcd19d1af64c07792aade0747b54e0f)
Reviewed-on: https://chromium-review.googlesource.com/566387
Reviewed-by: Kees Cook <keescook@chromium.org>
(cherry picked from commit 494ccded21eee9205143f34c294a67cfbeed61cc)
Reviewed-on: https://chromium-review.googlesource.com/681803
1 file changed
