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