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s390: limit brk randomization to 32MB

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[ 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: Stefan Liebler <stli@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
This commit is contained in:
Martin Schwidefsky 2019-03-04 12:33:28 +01:00 committed by Greg Kroah-Hartman
parent 93c2b843ca
commit 3b2c5114a6
1 changed files with 7 additions and 4 deletions
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11
arch/s390/include/asm/elf.h
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@ -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