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arm64: csum: Fix handling of bad packets 

Although iph is expected to point to at least 20 bytes of valid memory,
ihl may be bogus, for example on reception of a corrupt packet. If it
happens to be less than 5, we really don't want to run away and
dereference 16GB worth of memory until it wraps back to exactly zero...

Fixes: 0e455d8e80 ("arm64: Implement optimised IP checksum helpers")
Reported-by: guodeqing <geffrey.guo@huawei.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Robin Murphy 2020-07-30 10:56:49 +01:00 committed by Will Deacon
parent 835d1c3a98
commit 05fb3dbda1
1 changed files with 3 additions and 2 deletions
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5
arch/arm64/include/asm/checksum.h
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@ -24,16 +24,17 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
__uint128_t tmp;
u64 sum;
int n = ihl; /* we want it signed */
tmp = *(const __uint128_t *)iph;
iph += 16;
ihl -= 4;
n -= 4;
tmp += ((tmp >> 64) | (tmp << 64));
sum = tmp >> 64;
do {
sum += *(const u32 *)iph;
iph += 4;
} while (--ihl);
} while (--n > 0);
sum += ((sum >> 32) | (sum << 32));
return csum_fold((__force u32)(sum >> 32));