Commit c2c24edb authored Jan 17, 2020 by Robin Murphy Committed by Will Deacon Jan 17, 2020

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 <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

parent 5777eaed

arch/arm64/lib/csum.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -20,6 +20,9 @@ unsigned int do_csum(const unsigned char *buff, int len)
		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

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