netfilter: take care of timewait sockets

Sami Farin reported crashes in xt_LOG because it assumes skb->sk is a
full blown socket.

Since (41063e9 ipv4: Early TCP socket demux), we can have skb->sk
pointing to a timewait socket.

Same fix is needed in nfnetlink_log.

Diagnosed-by: Florian Westphal <fw@strlen.de>
Reported-by: Sami Farin <hvtaifwkbgefbaei@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

2 files changed, 25 insertions, 22 deletions

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 14e2f3903142..5cfb5bedb2b8 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -381,6 +381,7 @@ __build_packet_message(struct nfulnl_instance *inst,
         struct nlmsghdr *nlh;
         struct nfgenmsg *nfmsg;
         sk_buff_data_t old_tail = inst->skb->tail;
+        struct sock *sk;
 
         nlh = nlmsg_put(inst->skb, 0, 0,
                         NFNL_SUBSYS_ULOG << 8 | NFULNL_MSG_PACKET,
@@ -499,18 +500,19 @@ __build_packet_message(struct nfulnl_instance *inst,
         }
 
         /* UID */
-        if (skb->sk) {
-                read_lock_bh(&skb->sk->sk_callback_lock);
-                if (skb->sk->sk_socket && skb->sk->sk_socket->file) {
-                        struct file *file = skb->sk->sk_socket->file;
+        sk = skb->sk;
+        if (sk && sk->sk_state != TCP_TIME_WAIT) {
+                read_lock_bh(&sk->sk_callback_lock);
+                if (sk->sk_socket && sk->sk_socket->file) {
+                        struct file *file = sk->sk_socket->file;
                         __be32 uid = htonl(file->f_cred->fsuid);
                         __be32 gid = htonl(file->f_cred->fsgid);
-                        read_unlock_bh(&skb->sk->sk_callback_lock);
+                        read_unlock_bh(&sk->sk_callback_lock);
                         if (nla_put_be32(inst->skb, NFULA_UID, uid) ||
                             nla_put_be32(inst->skb, NFULA_GID, gid))
                                 goto nla_put_failure;
                 } else
-                        read_unlock_bh(&skb->sk->sk_callback_lock);
+                        read_unlock_bh(&sk->sk_callback_lock);
         }
 
         /* local sequence number */
diff --git a/net/netfilter/xt_LOG.c b/net/netfilter/xt_LOG.c
index ff5f75fddb15..2a4f9693e799 100644
--- a/net/netfilter/xt_LOG.c
+++ b/net/netfilter/xt_LOG.c
@@ -145,6 +145,19 @@ static int dump_tcp_header(struct sbuff *m, const struct sk_buff *skb,
         return 0;
 }
 
+static void dump_sk_uid_gid(struct sbuff *m, struct sock *sk)
+{
+        if (!sk || sk->sk_state == TCP_TIME_WAIT)
+                return;
+
+        read_lock_bh(&sk->sk_callback_lock);
+        if (sk->sk_socket && sk->sk_socket->file)
+                sb_add(m, "UID=%u GID=%u ",
+                        sk->sk_socket->file->f_cred->fsuid,
+                        sk->sk_socket->file->f_cred->fsgid);
+        read_unlock_bh(&sk->sk_callback_lock);
+}
+
 /* One level of recursion won't kill us */
 static void dump_ipv4_packet(struct sbuff *m,
                         const struct nf_loginfo *info,
@@ -361,14 +374,8 @@ static void dump_ipv4_packet(struct sbuff *m,
         }
 
         /* Max length: 15 "UID=4294967295 " */
-        if ((logflags & XT_LOG_UID) && !iphoff && skb->sk) {
-                read_lock_bh(&skb->sk->sk_callback_lock);
-                if (skb->sk->sk_socket && skb->sk->sk_socket->file)
-                        sb_add(m, "UID=%u GID=%u ",
-                                skb->sk->sk_socket->file->f_cred->fsuid,
-                                skb->sk->sk_socket->file->f_cred->fsgid);
-                read_unlock_bh(&skb->sk->sk_callback_lock);
-        }
+        if ((logflags & XT_LOG_UID) && !iphoff)
+                dump_sk_uid_gid(m, skb->sk);
 
         /* Max length: 16 "MARK=0xFFFFFFFF " */
         if (!iphoff && skb->mark)
@@ -717,14 +724,8 @@ static void dump_ipv6_packet(struct sbuff *m,
         }
 
         /* Max length: 15 "UID=4294967295 " */
-        if ((logflags & XT_LOG_UID) && recurse && skb->sk) {
-                read_lock_bh(&skb->sk->sk_callback_lock);
-                if (skb->sk->sk_socket && skb->sk->sk_socket->file)
-                        sb_add(m, "UID=%u GID=%u ",
-                                skb->sk->sk_socket->file->f_cred->fsuid,
-                                skb->sk->sk_socket->file->f_cred->fsgid);
-                read_unlock_bh(&skb->sk->sk_callback_lock);
-        }
+        if ((logflags & XT_LOG_UID) && recurse)
+                dump_sk_uid_gid(m, skb->sk);
 
         /* Max length: 16 "MARK=0xFFFFFFFF " */
         if (!recurse && skb->mark)