diff options
| author | Yann Droneaud <ydroneaud@opteya.com> | 2014-11-17 23:02:19 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-09-13 09:07:59 -0700 |
| commit | 82c9aed33b8a6ca79121d54f1504e9df6b0479cd (patch) | |
| tree | f38367970d4b6e78c68e3ce5c44ea72a4e20b7cd | |
| parent | d51689e20adbf8fe2c3999939da8d61ed2ccbc58 (diff) | |
arm64/mm: Remove hack in mmap randomize layout
commit d6c763afab142a85e4770b4bc2a5f40f256d5c5d upstream.
Since commit 8a0a9bd4db63 ('random: make get_random_int() more
random'), get_random_int() returns a random value for each call,
so comment and hack introduced in mmap_rnd() as part of commit
1d18c47c735e ('arm64: MMU fault handling and page table management')
are incorrects.
Commit 1d18c47c735e seems to use the same hack introduced by
commit a5adc91a4b44 ('powerpc: Ensure random space between stack
and mmaps'), latter copied in commit 5a0efea09f42 ('sparc64: Sharpen
address space randomization calculations.').
But both architectures were cleaned up as part of commit
fa8cbaaf5a68 ('powerpc+sparc64/mm: Remove hack in mmap randomize
layout') as hack is no more needed since commit 8a0a9bd4db63.
So the present patch removes the comment and the hack around
get_random_int() on AArch64's mmap_rnd().
Cc: David S. Miller <davem@davemloft.net>
Cc: Anton Blanchard <anton@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Dan McGee <dpmcgee@gmail.com>
Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Matthias Brugger <mbrugger@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/arm64/mm/mmap.c | 12 |
1 files changed, 2 insertions, 10 deletions
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 7c7be7855638..8aaf073ee078 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c @@ -47,22 +47,14 @@ static int mmap_is_legacy(void) return sysctl_legacy_va_layout; } -/* - * Since get_random_int() returns the same value within a 1 jiffy window, we - * will almost always get the same randomisation for the stack and mmap - * region. This will mean the relative distance between stack and mmap will be - * the same. - * - * To avoid this we can shift the randomness by 1 bit. - */ static unsigned long mmap_rnd(void) { unsigned long rnd = 0; if (current->flags & PF_RANDOMIZE) - rnd = (long)get_random_int() & (STACK_RND_MASK >> 1); + rnd = (long)get_random_int() & STACK_RND_MASK; - return rnd << (PAGE_SHIFT + 1); + return rnd << PAGE_SHIFT; } static unsigned long mmap_base(void) |