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| author | dcashman <dcashman@google.com> | 2015-12-29 15:44:12 -0800 |
|---|---|---|
| committer | Ziyan <jaraidaniel@gmail.com> | 2016-10-29 01:33:54 +0200 |
| commit | bfb69c912b280fdf56fcf2c26d8fc996cabc9f87 (patch) | |
| tree | 85c80647cbbe3d8050a5f3e093893ad7e616566b /arch/x86 | |
| parent | cd76a77c16e5b485c935aa1f21acda2142f8970d (diff) | |
| download | kernel_samsung_tuna-bfb69c912b280fdf56fcf2c26d8fc996cabc9f87.zip kernel_samsung_tuna-bfb69c912b280fdf56fcf2c26d8fc996cabc9f87.tar.gz kernel_samsung_tuna-bfb69c912b280fdf56fcf2c26d8fc996cabc9f87.tar.bz2 | |
FROMLIST: x86: mm: support ARCH_MMAP_RND_BITS.
(cherry picked from commit https://lkml.org/lkml/2015/12/21/339)
x86: arch_mmap_rnd() uses hard-coded values, 8 for 32-bit and 28 for
64-bit, to generate the random offset for the mmap base address.
This value represents a compromise between increased ASLR
effectiveness and avoiding address-space fragmentation. Replace it
with a Kconfig option, which is sensibly bounded, so that platform
developers may choose where to place this compromise. Keep default
values as new minimums.
Bug: 24047224
Signed-off-by: Daniel Cashman <dcashman@android.com>
Signed-off-by: Daniel Cashman <dcashman@google.com>
Change-Id: Id1fb53df5fedc909b79f3d952f120e6104900f24
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/Kconfig | 16 | ||||
| -rw-r--r-- | arch/x86/mm/mmap.c | 12 |
2 files changed, 22 insertions, 6 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 90bf314..383c7f9 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -70,6 +70,8 @@ config X86 select IRQ_FORCED_THREADING select USE_GENERIC_SMP_HELPERS if SMP select HAVE_BPF_JIT if (X86_64 && NET) + select HAVE_ARCH_MMAP_RND_BITS if MMU + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT config INSTRUCTION_DECODER def_bool (KPROBES || PERF_EVENTS) @@ -119,6 +121,20 @@ config ZONE_DMA If unsure, say Y. +config ARCH_MMAP_RND_BITS_MIN + default 28 if 64BIT + default 8 + +config ARCH_MMAP_RND_BITS_MAX + default 32 if 64BIT + default 16 + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + default 8 + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + default 16 + config SBUS bool diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index f927429..88bd010 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -81,15 +81,15 @@ static unsigned long mmap_rnd(void) { unsigned long rnd = 0; - /* - * 8 bits of randomness in 32bit mmaps, 20 address space bits - * 28 bits of randomness in 64bit mmaps, 40 address space bits - */ if (current->flags & PF_RANDOMIZE) { if (mmap_is_ia32()) - rnd = get_random_int() % (1<<8); +#ifdef CONFIG_COMPAT + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_compat_bits) - 1); +#else + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); +#endif else - rnd = get_random_int() % (1<<28); + rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); } return rnd << PAGE_SHIFT; } |