lib/checksum.c: use 32-bit arithmetic consistently (c44ba9f6) · Commits · 戴 / test

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>

lib/checksum.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -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;

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