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Commit 109c32ff authored by Matt Redfearn's avatar Matt Redfearn Committed by Ralf Baechle
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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: default avatarMatt Redfearn <matt.redfearn@imgtec.com>
Reviewed-by: default avatarKees 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: default avatarRalf Baechle <ralf@linux-mips.org>
parent d9ae4f18

arch/mips/Kconfig

+16 −0
Original line number Diff line number Diff line
@@ -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

arch/mips/mm/mmap.c

+5 −5
Original line number Diff line number Diff line
@@ -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)