diff options
| author | Willem de Bruijn <willemb@google.com> | 2018-07-24 02:36:48 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-07-25 02:35:58 +0300 |
| commit | 2efd4fca703a6707cad16ab486eaab8fc7f0fd49 (patch) | |
| tree | e288e1c6f4714415b8fae9088f6d48b89881ae94 | |
| parent | ae2dcb28c24794a87e424a726a1cf1a61980f52d (diff) | |
| download | linux-2efd4fca703a6707cad16ab486eaab8fc7f0fd49.tar.xz | |
ip: in cmsg IP(V6)_ORIGDSTADDR call pskb_may_pull
Syzbot reported a read beyond the end of the skb head when returning
IPV6_ORIGDSTADDR:
BUG: KMSAN: kernel-infoleak in put_cmsg+0x5ef/0x860 net/core/scm.c:242
CPU: 0 PID: 4501 Comm: syz-executor128 Not tainted 4.17.0+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x185/0x1d0 lib/dump_stack.c:113
kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1125
kmsan_internal_check_memory+0x138/0x1f0 mm/kmsan/kmsan.c:1219
kmsan_copy_to_user+0x7a/0x160 mm/kmsan/kmsan.c:1261
copy_to_user include/linux/uaccess.h:184 [inline]
put_cmsg+0x5ef/0x860 net/core/scm.c:242
ip6_datagram_recv_specific_ctl+0x1cf3/0x1eb0 net/ipv6/datagram.c:719
ip6_datagram_recv_ctl+0x41c/0x450 net/ipv6/datagram.c:733
rawv6_recvmsg+0x10fb/0x1460 net/ipv6/raw.c:521
[..]
This logic and its ipv4 counterpart read the destination port from
the packet at skb_transport_offset(skb) + 4.
With MSG_MORE and a local SOCK_RAW sender, syzbot was able to cook a
packet that stores headers exactly up to skb_transport_offset(skb) in
the head and the remainder in a frag.
Call pskb_may_pull before accessing the pointer to ensure that it lies
in skb head.
Link: http://lkml.kernel.org/r/CAF=yD-LEJwZj5a1-bAAj2Oy_hKmGygV6rsJ_WOrAYnv-fnayiQ@mail.gmail.com
Reported-by: syzbot+9adb4b567003cac781f0@syzkaller.appspotmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/ipv4/ip_sockglue.c | 7 | ||||
| -rw-r--r-- | net/ipv6/datagram.c | 7 |
2 files changed, 10 insertions, 4 deletions
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 64c76dcf7386..c0fe5ad996f2 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -150,15 +150,18 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb) { struct sockaddr_in sin; const struct iphdr *iph = ip_hdr(skb); - __be16 *ports = (__be16 *)skb_transport_header(skb); + __be16 *ports; + int end; - if (skb_transport_offset(skb) + 4 > (int)skb->len) + 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); sin.sin_family = AF_INET; sin.sin_addr.s_addr = iph->daddr; diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c index 2ee08b6a86a4..1a1f876f8e28 100644 --- a/net/ipv6/datagram.c +++ b/net/ipv6/datagram.c @@ -700,13 +700,16 @@ void ip6_datagram_recv_specific_ctl(struct sock *sk, struct msghdr *msg, } if (np->rxopt.bits.rxorigdstaddr) { struct sockaddr_in6 sin6; - __be16 *ports = (__be16 *) skb_transport_header(skb); + __be16 *ports; + int end; - if (skb_transport_offset(skb) + 4 <= (int)skb->len) { + end = skb_transport_offset(skb) + 4; + if (end <= 0 || pskb_may_pull(skb, end)) { /* 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; |