Commit 109c32ff authored Nov 24, 2016 by Matt Redfearn Committed by Ralf Baechle Jan 03, 2017

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>

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)

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