Commit 9af0c7a6 authored Nov 15, 2011 by Ludwig Nussel Committed by Ingo Molnar Dec 05, 2011

x86: Fix mmap random address range



On x86_32 casting the unsigned int result of get_random_int() to
long may result in a negative value.  On x86_32 the range of
mmap_rnd() therefore was -255 to 255.  The 32bit mode on x86_64
used 0 to 255 as intended.

The bug was introduced by 675a0813 ("x86: unify mmap_{32|64}.c")
in January 2008.

Signed-off-by: Ludwig Nussel <ludwig.nussel@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: harvey.harrison@gmail.com
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/201111152246.pAFMklOB028527@wpaz5.hot.corp.google.com


Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 17623915

arch/x86/mm/mmap.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -75,9 +75,9 @@ static unsigned long mmap_rnd(void)
		*/
		if (current->flags & PF_RANDOMIZE) {
		if (mmap_is_ia32())
		rnd = (long)get_random_int() % (1<<8);
		rnd = get_random_int() % (1<<8);
		else
		rnd = (long)(get_random_int() % (1<<28));
		rnd = get_random_int() % (1<<28);
		}
		return rnd << PAGE_SHIFT;
		}

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