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48 lines
1.5 KiB
Diff
48 lines
1.5 KiB
Diff
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From 34b2cef20f19c87999fff3da4071e66937db9644 Mon Sep 17 00:00:00 2001
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From: Eric Dumazet <edumazet@google.com>
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Date: Sat, 4 Feb 2017 11:16:52 -0800
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Subject: ipv4: keep skb->dst around in presence of IP options
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Andrey Konovalov got crashes in __ip_options_echo() when a NULL skb->dst
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is accessed.
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ipv4_pktinfo_prepare() should not drop the dst if (evil) IP options
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are present.
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We could refine the test to the presence of ts_needtime or srr,
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but IP options are not often used, so let's be conservative.
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Thanks to syzkaller team for finding this bug.
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Fixes: d826eb14ecef ("ipv4: PKTINFO doesnt need dst reference")
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Signed-off-by: Eric Dumazet <edumazet@google.com>
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Reported-by: Andrey Konovalov <andreyknvl@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 | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
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index 53ae0c6..9000117 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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@@ -1238,7 +1238,14 @@ void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb)
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pktinfo->ipi_ifindex = 0;
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pktinfo->ipi_spec_dst.s_addr = 0;
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}
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- skb_dst_drop(skb);
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+ /* We need to keep the dst for __ip_options_echo()
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+ * We could restrict the test to opt.ts_needtime || opt.srr,
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+ * but the following is good enough as IP options are not often used.
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+ */
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+ if (unlikely(IPCB(skb)->opt.optlen))
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+ skb_dst_force(skb);
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+ else
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+ skb_dst_drop(skb);
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}
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int ip_setsockopt(struct sock *sk, int level,
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--
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cgit v1.1
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