From: Ludwig Nussel <ludwig.nussel@suse.de>
Date: Wed, 24 Aug 2011 23:46:16 +0000 (+1000)
Subject: On x86_32 casting the unsigned int result of get_random_int() to long may
X-Git-Tag: next-20110912~1^2~140
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f940df367d4c14c2883ab8b894ba351624e9df2e;p=karo-tx-linux.git

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: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 4b5ba85eb5c9..845df6835f9f 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -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;
 }