Commit 47ac5484 authored Aug 15, 2017 by Oleg Nesterov Committed by Thomas Gleixner Aug 16, 2017

x86: Fix norandmaps/ADDR_NO_RANDOMIZE



Documentation/admin-guide/kernel-parameters.txt says:

    norandmaps  Don't use address space randomization. Equivalent
                to echo 0 > /proc/sys/kernel/randomize_va_space

but it doesn't work because arch_rnd() which is used to randomize
mm->mmap_base returns a random value unconditionally. And as Kirill
pointed out, ADDR_NO_RANDOMIZE is broken by the same reason.

Just shift the PF_RANDOMIZE check from arch_mmap_rnd() to arch_rnd().

Fixes: 1b028f78 ("x86/mm: Introduce mmap_compat_base() for 32-bit mmap()")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: stable@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20170815153952.GA1076@redhat.com

parent 84393817

arch/x86/mm/mmap.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -79,13 +79,13 @@ static int mmap_is_legacy(void)

		static unsigned long arch_rnd(unsigned int rndbits)
		{
		if (!(current->flags & PF_RANDOMIZE))
		return 0;
		return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
		}

		unsigned long arch_mmap_rnd(void)
		{
		if (!(current->flags & PF_RANDOMIZE))
		return 0;
		return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
		}

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