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tcp/dccp: fix another race at listener dismantle
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Ilya reported following lockdep splat:

kernel: =========================
kernel: [ BUG: held lock freed! ]
kernel: 4.5.0-rc1-ceph-00026-g5e0a311 #1 Not tainted
kernel: -------------------------
kernel: swapper/5/0 is freeing memory
ffff880035c9d200-ffff880035c9dbff, with a lock still held there!
kernel: (&(&queue->rskq_lock)->rlock){+.-...}, at:
[<ffffffff816f6a88>] inet_csk_reqsk_queue_add+0x28/0xa0
kernel: 4 locks held by swapper/5/0:
kernel: #0:  (rcu_read_lock){......}, at: [<ffffffff8169ef6b>]
netif_receive_skb_internal+0x4b/0x1f0
kernel: #1:  (rcu_read_lock){......}, at: [<ffffffff816e977f>]
ip_local_deliver_finish+0x3f/0x380
kernel: #2:  (slock-AF_INET){+.-...}, at: [<ffffffff81685ffb>]
sk_clone_lock+0x19b/0x440
kernel: #3:  (&(&queue->rskq_lock)->rlock){+.-...}, at:
[<ffffffff816f6a88>] inet_csk_reqsk_queue_add+0x28/0xa0

To properly fix this issue, inet_csk_reqsk_queue_add() needs
to return to its callers if the child as been queued
into accept queue.

We also need to make sure listener is still there before
calling sk->sk_data_ready(), by holding a reference on it,
since the reference carried by the child can disappear as
soon as the child is put on accept queue.

Reported-by: Ilya Dryomov <[email protected]>
Fixes: ebb516a ("tcp/dccp: fix race at listener dismantle phase")
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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@davem330
Eric Dumazet authored and davem330 committed Feb 18, 2016
1 parent deed49d commit 7716682
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Showing 6 changed files with 38 additions and 37 deletions.
5 changes: 3 additions & 2 deletions include/net/inet_connection_sock.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -270,8 +270,9 @@ struct dst_entry *inet_csk_route_child_sock(const struct sock *sk,
struct sock *newsk,
const struct request_sock *req);

void inet_csk_reqsk_queue_add(struct sock *sk, struct request_sock *req,
struct sock *child);
struct sock *inet_csk_reqsk_queue_add(struct sock *sk,
struct request_sock *req,
struct sock *child);
void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
unsigned long timeout);
struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
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14 changes: 7 additions & 7 deletions net/dccp/ipv4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -824,26 +824,26 @@ static int dccp_v4_rcv(struct sk_buff *skb)

if (sk->sk_state == DCCP_NEW_SYN_RECV) {
struct request_sock *req = inet_reqsk(sk);
struct sock *nsk = NULL;
struct sock *nsk;

sk = req->rsk_listener;
if (likely(sk->sk_state == DCCP_LISTEN)) {
nsk = dccp_check_req(sk, skb, req);
} else {
if (unlikely(sk->sk_state != DCCP_LISTEN)) {
inet_csk_reqsk_queue_drop_and_put(sk, req);
goto lookup;
}
sock_hold(sk);
nsk = dccp_check_req(sk, skb, req);
if (!nsk) {
reqsk_put(req);
goto discard_it;
goto discard_and_relse;
}
if (nsk == sk) {
sock_hold(sk);
reqsk_put(req);
} else if (dccp_child_process(sk, nsk, skb)) {
dccp_v4_ctl_send_reset(sk, skb);
goto discard_it;
goto discard_and_relse;
} else {
sock_put(sk);
return 0;
}
}
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14 changes: 7 additions & 7 deletions net/dccp/ipv6.c
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Original file line number Diff line number Diff line change
Expand Up @@ -691,26 +691,26 @@ static int dccp_v6_rcv(struct sk_buff *skb)

if (sk->sk_state == DCCP_NEW_SYN_RECV) {
struct request_sock *req = inet_reqsk(sk);
struct sock *nsk = NULL;
struct sock *nsk;

sk = req->rsk_listener;
if (likely(sk->sk_state == DCCP_LISTEN)) {
nsk = dccp_check_req(sk, skb, req);
} else {
if (unlikely(sk->sk_state != DCCP_LISTEN)) {
inet_csk_reqsk_queue_drop_and_put(sk, req);
goto lookup;
}
sock_hold(sk);
nsk = dccp_check_req(sk, skb, req);
if (!nsk) {
reqsk_put(req);
goto discard_it;
goto discard_and_relse;
}
if (nsk == sk) {
sock_hold(sk);
reqsk_put(req);
} else if (dccp_child_process(sk, nsk, skb)) {
dccp_v6_ctl_send_reset(sk, skb);
goto discard_it;
goto discard_and_relse;
} else {
sock_put(sk);
return 0;
}
}
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14 changes: 7 additions & 7 deletions net/ipv4/inet_connection_sock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -789,14 +789,16 @@ static void inet_child_forget(struct sock *sk, struct request_sock *req,
reqsk_put(req);
}

void inet_csk_reqsk_queue_add(struct sock *sk, struct request_sock *req,
struct sock *child)
struct sock *inet_csk_reqsk_queue_add(struct sock *sk,
struct request_sock *req,
struct sock *child)
{
struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;

spin_lock(&queue->rskq_lock);
if (unlikely(sk->sk_state != TCP_LISTEN)) {
inet_child_forget(sk, req, child);
child = NULL;
} else {
req->sk = child;
req->dl_next = NULL;
Expand All @@ -808,6 +810,7 @@ void inet_csk_reqsk_queue_add(struct sock *sk, struct request_sock *req,
sk_acceptq_added(sk);
}
spin_unlock(&queue->rskq_lock);
return child;
}
EXPORT_SYMBOL(inet_csk_reqsk_queue_add);

Expand All @@ -817,11 +820,8 @@ struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
if (own_req) {
inet_csk_reqsk_queue_drop(sk, req);
reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, 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;
if (inet_csk_reqsk_queue_add(sk, req, child))
return child;
}
/* Too bad, another child took ownership of the request, undo. */
bh_unlock_sock(child);
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14 changes: 7 additions & 7 deletions net/ipv4/tcp_ipv4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1597,30 +1597,30 @@ int tcp_v4_rcv(struct sk_buff *skb)

if (sk->sk_state == TCP_NEW_SYN_RECV) {
struct request_sock *req = inet_reqsk(sk);
struct sock *nsk = NULL;
struct sock *nsk;

sk = req->rsk_listener;
if (unlikely(tcp_v4_inbound_md5_hash(sk, skb))) {
reqsk_put(req);
goto discard_it;
}
if (likely(sk->sk_state == TCP_LISTEN)) {
nsk = tcp_check_req(sk, skb, req, false);
} else {
if (unlikely(sk->sk_state != TCP_LISTEN)) {
inet_csk_reqsk_queue_drop_and_put(sk, req);
goto lookup;
}
sock_hold(sk);
nsk = tcp_check_req(sk, skb, req, false);
if (!nsk) {
reqsk_put(req);
goto discard_it;
goto discard_and_relse;
}
if (nsk == sk) {
sock_hold(sk);
reqsk_put(req);
} else if (tcp_child_process(sk, nsk, skb)) {
tcp_v4_send_reset(nsk, skb);
goto discard_it;
goto discard_and_relse;
} else {
sock_put(sk);
return 0;
}
}
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14 changes: 7 additions & 7 deletions net/ipv6/tcp_ipv6.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1387,32 +1387,32 @@ static int tcp_v6_rcv(struct sk_buff *skb)

if (sk->sk_state == TCP_NEW_SYN_RECV) {
struct request_sock *req = inet_reqsk(sk);
struct sock *nsk = NULL;
struct sock *nsk;

sk = req->rsk_listener;
tcp_v6_fill_cb(skb, hdr, th);
if (tcp_v6_inbound_md5_hash(sk, skb)) {
reqsk_put(req);
goto discard_it;
}
if (likely(sk->sk_state == TCP_LISTEN)) {
nsk = tcp_check_req(sk, skb, req, false);
} else {
if (unlikely(sk->sk_state != TCP_LISTEN)) {
inet_csk_reqsk_queue_drop_and_put(sk, req);
goto lookup;
}
sock_hold(sk);
nsk = tcp_check_req(sk, skb, req, false);
if (!nsk) {
reqsk_put(req);
goto discard_it;
goto discard_and_relse;
}
if (nsk == sk) {
sock_hold(sk);
reqsk_put(req);
tcp_v6_restore_cb(skb);
} else if (tcp_child_process(sk, nsk, skb)) {
tcp_v6_send_reset(nsk, skb);
goto discard_it;
goto discard_and_relse;
} else {
sock_put(sk);
return 0;
}
}
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