Message ID | 1486235812.21871.145.camel@edumazet-glaptop3.roam.corp.google.com |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
From: Eric Dumazet <eric.dumazet@gmail.com> Date: Sat, 04 Feb 2017 11:16:52 -0800 > From: Eric Dumazet <edumazet@google.com> > > Andrey Konovalov got crashes in __ip_options_echo() when a NULL skb->dst > is accessed. > > ipv4_pktinfo_prepare() should not drop the dst if (evil) IP options > are present. > > We could refine the test to the presence of ts_needtime or srr, > but IP options are not often used, so let's be conservative. > > Thanks to syzkaller team for finding this bug. > > Fixes: d826eb14ecef ("ipv4: PKTINFO doesnt need dst reference") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Reported-by: Andrey Konovalov <andreyknvl@google.com> Applied and queued up for -stable, thanks.
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 8a4409dd390aac7fcb88383af1550a2f967d..c4fcf9d713cca64a3afaec1628692739d9fa 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1243,7 +1243,14 @@ void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb) pktinfo->ipi_ifindex = 0; pktinfo->ipi_spec_dst.s_addr = 0; } - skb_dst_drop(skb); + /* We need to keep the dst for __ip_options_echo() + * We could restrict the test to opt.ts_needtime || opt.srr, + * but the following is good enough as IP options are not often used. + */ + if (unlikely(IPCB(skb)->opt.optlen)) + skb_dst_force(skb); + else + skb_dst_drop(skb); } int ip_setsockopt(struct sock *sk, int level,