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authorEric Dumazet <edumazet@google.com>2019-01-04 11:00:00 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-01-22 21:40:35 +0100
commita72e572f8a2d61db2f4d17e1de17fb92573870ef (patch)
tree66ae439f9c227ccffb91cdbe1ff0808da77a74de
parent341906cb25f9b8355183518769c14e9ea240aa52 (diff)
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ipv6: make icmp6_send() robust against null skb->dev
commit 8d933670452107e41165bea70a30dffbd281bef1 upstream. syzbot was able to crash one host with the following stack trace : kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 8625 Comm: syz-executor4 Not tainted 4.20.0+ #8 RIP: 0010:dev_net include/linux/netdevice.h:2169 [inline] RIP: 0010:icmp6_send+0x116/0x2d30 net/ipv6/icmp.c:426 icmpv6_send smack_socket_sock_rcv_skb security_sock_rcv_skb sk_filter_trim_cap __sk_receive_skb dccp_v6_do_rcv release_sock This is because a RX packet found socket owned by user and was stored into socket backlog. Before leaving RCU protected section, skb->dev was cleared in __sk_receive_skb(). When socket backlog was finally handled at release_sock() time, skb was fed to smack_socket_sock_rcv_skb() then icmp6_send() We could fix the bug in smack_socket_sock_rcv_skb(), or simply make icmp6_send() more robust against such possibility. In the future we might provide to icmp6_send() the net pointer instead of infering it. Fixes: d66a8acbda92 ("Smack: Inform peer that IPv6 traffic has been blocked") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Piotr Sawicki <p.sawicki2@partner.samsung.com> Cc: Casey Schaufler <casey@schaufler-ca.com> Reported-by: syzbot <syzkaller@googlegroups.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/ipv6/icmp.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index c9c53ade55c3..6d14cbe443f8 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -421,10 +421,10 @@ static int icmp6_iif(const struct sk_buff *skb)
static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
const struct in6_addr *force_saddr)
{
- struct net *net = dev_net(skb->dev);
struct inet6_dev *idev = NULL;
struct ipv6hdr *hdr = ipv6_hdr(skb);
struct sock *sk;
+ struct net *net;
struct ipv6_pinfo *np;
const struct in6_addr *saddr = NULL;
struct dst_entry *dst;
@@ -435,12 +435,16 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
int iif = 0;
int addr_type = 0;
int len;
- u32 mark = IP6_REPLY_MARK(net, skb->mark);
+ u32 mark;
if ((u8 *)hdr < skb->head ||
(skb_network_header(skb) + sizeof(*hdr)) > skb_tail_pointer(skb))
return;
+ if (!skb->dev)
+ return;
+ net = dev_net(skb->dev);
+ mark = IP6_REPLY_MARK(net, skb->mark);
/*
* Make sure we respect the rules
* i.e. RFC 1885 2.4(e)