From: Robin Murphy Date: Fri, 17 Jan 2020 15:48:39 +0000 Subject: [PATCH] arm64: csum: Fix pathological zero-length calls In validating the checksumming results of the new routine, I sadly neglected to test its not-checksumming results. Thus it slipped through that the one case where @buff is already dword-aligned and @len = 0 manages to defeat the tail-masking logic and behave as if @len = 8. For a zero length it doesn't make much sense to deference @buff anyway, so just add an early return (which has essentially zero impact on performance). Signed-off-by: Robin Murphy Signed-off-by: Will Deacon --- --- a/arch/arm64/lib/csum.c +++ b/arch/arm64/lib/csum.c @@ -20,6 +20,9 @@ unsigned int do_csum(const unsigned char const u64 *ptr; u64 data, sum64 = 0; + if (unlikely(len == 0)) + return 0; + offset = (unsigned long)buff & 7; /* * This is to all intents and purposes safe, since rounding down cannot