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Commit 3b2c5114 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Greg Kroah-Hartman
Browse files

s390: limit brk randomization to 32MB 



[ Upstream commit cd479eccd2e057116d504852814402a1e68ead80 ]

For a 64-bit process the randomization of the program break is quite
large with 1GB. That is as big as the randomization of the anonymous
mapping base, for a test case started with '/lib/ld64.so.1 <exec>'
it can happen that the heap is placed after the stack. To avoid
this limit the program break randomization to 32MB for 64-bit and
keep 8MB for 31-bit.

Reported-by: default avatarStefan Liebler <stli@linux.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarSasha Levin (Microsoft) <sashal@kernel.org>
parent 93c2b843

arch/s390/include/asm/elf.h

+7 −4
Original line number Diff line number Diff line
@@ -252,11 +252,14 @@ do { \ 


/*

 * Cache aliasing on the latest machines calls for a mapping granularity

 * of 512KB. For 64-bit processes use a 512KB alignment and a randomization

 * of up to 1GB. For 31-bit processes the virtual address space is limited,

 * use no alignment and limit the randomization to 8MB.

 * of 512KB for the anonymous mapping base. For 64-bit processes use a

 * 512KB alignment and a randomization of up to 1GB. For 31-bit processes

 * the virtual address space is limited, use no alignment and limit the

 * randomization to 8MB.

 * For the additional randomization of the program break use 32MB for

 * 64-bit and 8MB for 31-bit.

 */

#define BRK_RND_MASK	(is_compat_task() ? 0x7ffUL : 0x3ffffUL)

#define BRK_RND_MASK	(is_compat_task() ? 0x7ffUL : 0x1fffUL)

#define MMAP_RND_MASK	(is_compat_task() ? 0x7ffUL : 0x3ff80UL)

#define MMAP_ALIGN_MASK	(is_compat_task() ? 0 : 0x7fUL)

#define STACK_RND_MASK	MMAP_RND_MASK