From: Peter Williams <pwil3058@bigpond.net.au>
Date: Fri, 3 Feb 2006 11:04:33 +0000 (-0800)
Subject: [PATCH] lib: Fix bug in int_sqrt() for 64 bit longs
X-Git-Tag: v2.6.16-rc3~240
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f0c00257d63463fa9d692e632fae037d6c0e67b0;p=linux-2.6

[PATCH] lib: Fix bug in int_sqrt() for 64 bit longs

The implementation of int_sqrt() assumes that longs have 32 bits.  On
systems that have 64 bit longs this will result in gross errors when the
argument to the function is greater than 2^32 - 1 on such systems.  I doubt
whether any such use is currently made of int_sqrt() but the attached patch
fixes the problem anyway.

Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c
index a5d2cdc568..fd355a9932 100644
--- a/lib/int_sqrt.c
+++ b/lib/int_sqrt.c
@@ -15,7 +15,7 @@ unsigned long int_sqrt(unsigned long x)
 	op = x;
 	res = 0;
 
-	one = 1 << 30;
+	one = 1UL << (BITS_PER_LONG - 2);
 	while (one > op)
 		one >>= 2;