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ip: on queued skb use skb_header_pointer instead of pskb_may_pull 

Commit 2efd4fca70 ("ip: in cmsg IP(V6)_ORIGDSTADDR call
pskb_may_pull") avoided a read beyond the end of the skb linear
segment by calling pskb_may_pull.

That function can trigger a BUG_ON in pskb_expand_head if the skb is
shared, which it is when when peeking. It can also return ENOMEM.

Avoid both by switching to safer skb_header_pointer.

Fixes: 2efd4fca70 ("ip: in cmsg IP(V6)_ORIGDSTADDR call pskb_may_pull")
Reported-by: syzbot <syzkaller@googlegroups.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
Willem de Bruijn 2019-01-07 16:47:33 -05:00 committed by David S. Miller
parent 0b7959b625
commit 4a06fa67c4
2 changed files with 9 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
net/ipv4/ip_sockglue.c
View File

@ -148,19 +148,17 @@ static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
{
__be16 _ports[2], *ports;
struct sockaddr_in sin;
__be16 *ports;
int end;
end = skb_transport_offset(skb) + 4;
if (end > 0 && !pskb_may_pull(skb, end))
return;
/* All current transport protocols have the port numbers in the
* first four bytes of the transport header and this function is
* written with this assumption in mind.
*/
ports = (__be16 *)skb_transport_header(skb);
ports = skb_header_pointer(skb, skb_transport_offset(skb),
sizeof(_ports), &_ports);
if (!ports)
return;
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = ip_hdr(skb)->daddr;

10
net/ipv6/datagram.c
View File

@ -700,17 +700,15 @@ void ip6_datagram_recv_specific_ctl(struct sock *sk, struct msghdr *msg,
}
if (np->rxopt.bits.rxorigdstaddr) {
struct sockaddr_in6 sin6;
__be16 *ports;
int end;
__be16 _ports[2], *ports;
end = skb_transport_offset(skb) + 4;
if (end <= 0 || pskb_may_pull(skb, end)) {
ports = skb_header_pointer(skb, skb_transport_offset(skb),
sizeof(_ports), &_ports);
if (ports) {
/* All current transport protocols have the port numbers in the
* first four bytes of the transport header and this function is
* written with this assumption in mind.
*/
ports = (__be16 *)skb_transport_header(skb);
sin6.sin6_family = AF_INET6;
sin6.sin6_addr = ipv6_hdr(skb)->daddr;
sin6.sin6_port = ports[1];