path: root/arch
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authorAndrey Ryabinin <a.ryabinin@samsung.com>2015-03-20 15:42:27 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-05-06 21:56:21 +0200
commite26c761f5a57dc335748b2e730e89925744ce6c5 (patch)
treebb3c49e8311292feb38ac7a37e3690f050a02c2b /arch
parent7aea358e5c37d8f17e3911f21bd555d5533be7ec (diff)
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')
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