LoongArch: csum: Fix OoB access in IP checksum code for negative lengths

Commit 69e3a6a ("LoongArch: Add checksum optimization for 64-bit
system") would cause an undefined shift and an out-of-bounds read.

Commit 8bd795f ("arm64: csum: Fix OoB access in IP checksum code
for negative lengths") fixes the same issue on ARM64.

Fixes: 69e3a6a ("LoongArch: Add checksum optimization for 64-bit system")
Co-developed-by: Wentao Guan <[email protected]>
Signed-off-by: Wentao Guan <[email protected]>
Signed-off-by: Yuli Wang <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>

Author: Avenger-285714

arch/loongarch/lib/csum.c

@@ -25,7 +25,7 @@ unsigned int __no_sanitize_address do_csum(const unsigned char *buff, int len)
 	const u64 *ptr;
 	u64 data, sum64 = 0;
 
-	if (unlikely(len == 0))
+	if (unlikely(len <= 0))
 		return 0;
 
 	offset = (unsigned long)buff & 7;