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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 675a081 ("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>
This commit is contained in:
Ludwig Nussel 2011-11-15 14:46:46 -08:00 committed by Ingo Molnar
parent 1762391530
commit 9af0c7a6fa
1 changed files with 2 additions and 2 deletions
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4
arch/x86/mm/mmap.c
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@ -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;
}