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49 lines
1.5 KiB
Diff
49 lines
1.5 KiB
Diff
From ca4ef4574f1ee5252e2cd365f8f5d5bafd048f32 Mon Sep 17 00:00:00 2001
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From: Paolo Abeni <pabeni@redhat.com>
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Date: Tue, 21 Feb 2017 09:33:18 +0100
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Subject: ip: fix IP_CHECKSUM handling
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The skbs processed by ip_cmsg_recv() are not guaranteed to
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be linear e.g. when sending UDP packets over loopback with
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MSGMORE.
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Using csum_partial() on [potentially] the whole skb len
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is dangerous; instead be on the safe side and use skb_checksum().
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Thanks to syzkaller team to detect the issue and provide the
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reproducer.
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v1 -> v2:
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- move the variable declaration in a tighter scope
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Fixes: ad6f939ab193 ("ip: Add offset parameter to ip_cmsg_recv")
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Reported-by: Andrey Konovalov <andreyknvl@google.com>
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Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Acked-by: Eric Dumazet <edumazet@google.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/ipv4/ip_sockglue.c | 8 ++++----
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1 file changed, 4 insertions(+), 4 deletions(-)
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diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
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index ce1386a..ebd953b 100644
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--- a/net/ipv4/ip_sockglue.c
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+++ b/net/ipv4/ip_sockglue.c
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@@ -116,10 +116,10 @@ static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,
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if (skb->ip_summed != CHECKSUM_COMPLETE)
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return;
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- if (offset != 0)
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- csum = csum_sub(csum,
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- csum_partial(skb_transport_header(skb) + tlen,
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- offset, 0));
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+ if (offset != 0) {
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+ int tend_off = skb_transport_offset(skb) + tlen;
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+ csum = csum_sub(csum, skb_checksum(skb, tend_off, offset, 0));
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+ }
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put_cmsg(msg, SOL_IP, IP_CHECKSUM, sizeof(__wsum), &csum);
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}
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--
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cgit v1.1
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