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lib/checksum.c: use 32-bit arithmetic consistently

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The use of 'unsigned long' variables in the 32-bit part of do_csum()
is confusing at best, and potentially broken for long input on 64-bit
machines.

This changes the code to use 'unsigned int' instead, which makes
the code behave in the same (correct) way on both 32 and 64 bit
machines.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Arnd Bergmann 2009-06-23 21:22:58 +02:00
parent b6727b12dd
commit c44ba9f668
1 changed files with 4 additions and 4 deletions
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8
lib/checksum.c
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@ -37,7 +37,7 @@
#include <asm/byteorder.h>
static inline unsigned short from32to16(unsigned long x)
static inline unsigned short from32to16(unsigned int x)
{
/* add up 16-bit and 16-bit for 16+c bit */
x = (x & 0xffff) + (x >> 16);
@ -49,7 +49,7 @@ static inline unsigned short from32to16(unsigned long x)
static unsigned int do_csum(const unsigned char *buff, int len)
{
int odd, count;
unsigned long result = 0;
unsigned int result = 0;
if (len <= 0)
goto out;
@ -73,9 +73,9 @@ static unsigned int do_csum(const unsigned char *buff, int len)
}
count >>= 1; /* nr of 32-bit words.. */
if (count) {
unsigned long carry = 0;
unsigned int carry = 0;
do {
unsigned long w = *(unsigned int *) buff;
unsigned int w = *(unsigned int *) buff;
count--;
buff += 4;
result += carry;