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| author | Andrey Ryabinin <a.ryabinin@samsung.com> | 2015-03-20 15:42:27 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-05-06 21:56:21 +0200 |
| commit | e26c761f5a57dc335748b2e730e89925744ce6c5 (patch) | |
| tree | bb3c49e8311292feb38ac7a37e3690f050a02c2b /arch | |
| parent | 7aea358e5c37d8f17e3911f21bd555d5533be7ec (diff) | |
| download | lwn-e26c761f5a57dc335748b2e730e89925744ce6c5.tar.gz lwn-e26c761f5a57dc335748b2e730e89925744ce6c5.zip | |
ARM: 8320/1: fix integer overflow in ELF_ET_DYN_BASE
commit 8defb3367fcd19d1af64c07792aade0747b54e0f upstream.
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@samsung.com>
Reported-by: Maria Guseva <m.guseva@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/include/asm/elf.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h index 56211f2084ef..ce6e30628cc1 100644 --- a/arch/arm/include/asm/elf.h +++ b/arch/arm/include/asm/elf.h @@ -116,7 +116,7 @@ int dump_task_regs(struct task_struct *t, elf_gregset_t *elfregs); the loader. We need to make sure that it is out of the way of the program that it will "exec", and that there is sufficient room for the brk. */ -#define ELF_ET_DYN_BASE (2 * TASK_SIZE / 3) +#define ELF_ET_DYN_BASE (TASK_SIZE / 3 * 2) /* When the program starts, a1 contains a pointer to a function to be registered with atexit, as per the SVR4 ABI. A value of 0 means we |