[added to the 3.18 stable tree] ARM: 8320/1: fix integer overflow in ELF_ET_DYN_BASE

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



From: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>

This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 8defb3367fcd19d1af64c07792aade0747b54e0f ]

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
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
 arch/arm/include/asm/elf.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
index afb9caf..674d03f 100644
--- a/arch/arm/include/asm/elf.h
+++ b/arch/arm/include/asm/elf.h
@@ -115,7 +115,7 @@ 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 
-- 
2.1.0

--
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




[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]