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MIPS: Add support for ARCH_MMAP_RND_{COMPAT_}BITS 

arch_mmap_rnd() uses hard-coded limits of 16MB for the randomisation
of mmap within 32bit processes and 256MB in 64bit processes. Since v4.4
other arches support tuning this value in /proc/sys/vm/mmap_rnd_bits.
Add support for this to MIPS.

Set the minimum(default) number of bits randomisation for 32bit to 8 -
which with 4k pagesize is unchanged from the current 16MB total
randomness. The minimum(default) for 64bit is 12bits, again with 4k
pagesize this is the same as the current 256MB.

This patch is necessary for MIPS32 to pass the Android CTS tests, with
the number of random bits set to 15.

Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Daniel Cashman <dcashman@android.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mips@linux-mips.org
Cc: kernel-hardening@lists.openwall.com
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14617/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Matt Redfearn 2016-11-24 17:32:45 +00:00 committed by Ralf Baechle
parent d9ae4f18c0
commit 109c32ffd8
2 changed files with 21 additions and 5 deletions
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16
arch/mips/Kconfig
View File

@ -14,6 +14,8 @@ config MIPS
select HAVE_PERF_EVENTS
select PERF_USE_VMALLOC
select HAVE_ARCH_KGDB
select HAVE_ARCH_MMAP_RND_BITS if MMU
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_CBPF_JIT if !CPU_MICROMIPS
@ -3073,6 +3075,20 @@ config MMU
bool
default y
config ARCH_MMAP_RND_BITS_MIN
default 12 if 64BIT
default 8
config ARCH_MMAP_RND_BITS_MAX
default 18 if 64BIT
default 15
config ARCH_MMAP_RND_COMPAT_BITS_MIN
default 8
config ARCH_MMAP_RND_COMPAT_BITS_MAX
default 15
config I8253
bool
select CLKSRC_I8253

10
arch/mips/mm/mmap.c
View File

@ -146,14 +146,14 @@ unsigned long arch_mmap_rnd(void)
{
unsigned long rnd;
rnd = get_random_long();
rnd <<= PAGE_SHIFT;
#ifdef CONFIG_COMPAT
if (TASK_IS_32BIT_ADDR)
rnd &= 0xfffffful;
rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
else
rnd &= 0xffffffful;
#endif /* CONFIG_COMPAT */
rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
return rnd;
return rnd << PAGE_SHIFT;
}
void arch_pick_mmap_layout(struct mm_struct *mm)