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| author | Eric Dumazet <edumazet@google.com> | 2019-01-04 11:00:00 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2019-01-04 13:40:03 -0800 |
| commit | 8d933670452107e41165bea70a30dffbd281bef1 (patch) | |
| tree | 425c7c700f094383c2cf4dc84c19ed814b2d7494 /net/ipv6/icmp.c | |
| parent | 3271a4821882a64214acc1bd7b173900ec70c9bf (diff) | |
| download | lwn-8d933670452107e41165bea70a30dffbd281bef1.tar.gz lwn-8d933670452107e41165bea70a30dffbd281bef1.zip | |
ipv6: make icmp6_send() robust against null skb->dev
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>
Diffstat (limited to 'net/ipv6/icmp.c')
| -rw-r--r-- | net/ipv6/icmp.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c index 5d7aa2c2770c..bbcdfd299692 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -423,10 +423,10 @@ 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; @@ -437,12 +437,16 @@ 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) |