path: root/net/ipv4/ip_sockglue.c
diff options
authorWillem de Bruijn <willemb@google.com>2018-07-23 19:36:48 -0400
committerDavid S. Miller <davem@davemloft.net>2018-07-24 16:35:58 -0700
commit2efd4fca703a6707cad16ab486eaab8fc7f0fd49 (patch)
treee288e1c6f4714415b8fae9088f6d48b89881ae94 /net/ipv4/ip_sockglue.c
parentbnx2x: Fix invalid memory access in rss hash config path. (diff)
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>
Diffstat (limited to 'net/ipv4/ip_sockglue.c')
1 files changed, 5 insertions, 2 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))
/* 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;