| Message ID | 20170825132837.11287-2-kleber.souza@canonical.com |
|---|---|
| State | New |
| Headers | show |
On 25.08.2017 15:28, Kleber Sacilotto de Souza wrote: > From: Eric Dumazet <edumazet@google.com> > > CVE-2017-5970 > > 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> > Signed-off-by: David S. Miller <davem@davemloft.net> > (cherry picked from commit 34b2cef20f19c87999fff3da4071e66937db9644) > Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> Acked-by: Stefan Bader <stefan.bader@canonical.com> > --- > net/ipv4/ip_sockglue.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c > index 4aeb2131242b..b86d12793328 100644 > --- a/net/ipv4/ip_sockglue.c > +++ b/net/ipv4/ip_sockglue.c > @@ -1080,7 +1080,14 @@ 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, >
On 25/08/17 14:28, Kleber Sacilotto de Souza wrote: > From: Eric Dumazet <edumazet@google.com> > > CVE-2017-5970 > > 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> > Signed-off-by: David S. Miller <davem@davemloft.net> > (cherry picked from commit 34b2cef20f19c87999fff3da4071e66937db9644) > Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> > --- > net/ipv4/ip_sockglue.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c > index 4aeb2131242b..b86d12793328 100644 > --- a/net/ipv4/ip_sockglue.c > +++ b/net/ipv4/ip_sockglue.c > @@ -1080,7 +1080,14 @@ 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, > Acked-by: Colin Ian King <colin.king@canonical.com>
Applied to trusty/master-next branch. Thanks.
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 4aeb2131242b..b86d12793328 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1080,7 +1080,14 @@ 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,