inet: fix possible panic in reqsk_queue_unlink()
[ 3897.923145] BUG: unable to handle kernel NULL pointer dereference at
0000000000000080
[ 3897.931025] IP: [<ffffffffa9f27686>] reqsk_timer_handler+0x1a6/0x243
There is a race when reqsk_timer_handler() and tcp_check_req() call
inet_csk_reqsk_queue_unlink() on the same req at the same time.
Before commit fa76ce7328b2 ("inet: get rid of central tcp/dccp listener
timer"), listener spinlock was held and race could not happen.
To solve this bug, we change reqsk_queue_unlink() to not assume req
must be found, and we return a status, to conditionally release a
refcount on the request sock.
This also means tcp_check_req() in non fastopen case might or not
consume req refcount, so tcp_v6_hnd_req() & tcp_v4_hnd_req() have
to properly handle this.
(Same remark for dccp_check_req() and its callers)
inet_csk_reqsk_queue_drop() is now too big to be inlined, as it is
called 4 times in tcp and 3 times in dccp.
Fixes: fa76ce7328b2 ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 2b4f21d..ccf4c56 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -453,7 +453,8 @@
iph->saddr, iph->daddr);
if (req) {
nsk = dccp_check_req(sk, skb, req);
- reqsk_put(req);
+ if (!nsk)
+ reqsk_put(req);
return nsk;
}
nsk = inet_lookup_established(sock_net(sk), &dccp_hashinfo,
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 9d05510..5165571 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -301,7 +301,8 @@
&iph->daddr, inet6_iif(skb));
if (req) {
nsk = dccp_check_req(sk, skb, req);
- reqsk_put(req);
+ if (!nsk)
+ reqsk_put(req);
return nsk;
}
nsk = __inet6_lookup_established(sock_net(sk), &dccp_hashinfo,
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 5f56666..30addee 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -186,8 +186,7 @@
if (child == NULL)
goto listen_overflow;
- inet_csk_reqsk_queue_unlink(sk, req);
- inet_csk_reqsk_queue_removed(sk, req);
+ inet_csk_reqsk_queue_drop(sk, req);
inet_csk_reqsk_queue_add(sk, req, child);
out:
return child;
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 5c3dd62..8976ca4 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -564,6 +564,40 @@
}
EXPORT_SYMBOL(inet_rtx_syn_ack);
+/* return true if req was found in the syn_table[] */
+static bool reqsk_queue_unlink(struct request_sock_queue *queue,
+ struct request_sock *req)
+{
+ struct listen_sock *lopt = queue->listen_opt;
+ struct request_sock **prev;
+ bool found = false;
+
+ spin_lock(&queue->syn_wait_lock);
+
+ for (prev = &lopt->syn_table[req->rsk_hash]; *prev != NULL;
+ prev = &(*prev)->dl_next) {
+ if (*prev == req) {
+ *prev = req->dl_next;
+ found = true;
+ break;
+ }
+ }
+
+ spin_unlock(&queue->syn_wait_lock);
+ if (del_timer(&req->rsk_timer))
+ reqsk_put(req);
+ return found;
+}
+
+void inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req)
+{
+ if (reqsk_queue_unlink(&inet_csk(sk)->icsk_accept_queue, req)) {
+ reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
+ reqsk_put(req);
+ }
+}
+EXPORT_SYMBOL(inet_csk_reqsk_queue_drop);
+
static void reqsk_timer_handler(unsigned long data)
{
struct request_sock *req = (struct request_sock *)data;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 3571f2b..fc1c658 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1348,7 +1348,8 @@
req = inet_csk_search_req(sk, th->source, iph->saddr, iph->daddr);
if (req) {
nsk = tcp_check_req(sk, skb, req, false);
- reqsk_put(req);
+ if (!nsk)
+ reqsk_put(req);
return nsk;
}
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 63d6311..e5d7649 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -755,10 +755,11 @@
if (!child)
goto listen_overflow;
- inet_csk_reqsk_queue_unlink(sk, req);
- inet_csk_reqsk_queue_removed(sk, req);
-
+ inet_csk_reqsk_queue_drop(sk, req);
inet_csk_reqsk_queue_add(sk, req, child);
+ /* Warning: caller must not call reqsk_put(req);
+ * child stole last reference on it.
+ */
return child;
listen_overflow:
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ad51df8..b6575d6 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -946,7 +946,8 @@
&ipv6_hdr(skb)->daddr, tcp_v6_iif(skb));
if (req) {
nsk = tcp_check_req(sk, skb, req, false);
- reqsk_put(req);
+ if (!nsk)
+ reqsk_put(req);
return nsk;
}
nsk = __inet6_lookup_established(sock_net(sk), &tcp_hashinfo,