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 commitfa76ce7328
("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:fa76ce7328
("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>
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1d8dc3d3c8
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@ -279,12 +279,6 @@ static inline void inet_csk_reqsk_queue_add(struct sock *sk,
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void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
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unsigned long timeout);
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static inline void inet_csk_reqsk_queue_removed(struct sock *sk,
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struct request_sock *req)
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{
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reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
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}
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static inline void inet_csk_reqsk_queue_added(struct sock *sk,
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const unsigned long timeout)
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{
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@ -306,19 +300,7 @@ static inline int inet_csk_reqsk_queue_is_full(const struct sock *sk)
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return reqsk_queue_is_full(&inet_csk(sk)->icsk_accept_queue);
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}
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static inline void inet_csk_reqsk_queue_unlink(struct sock *sk,
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struct request_sock *req)
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{
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reqsk_queue_unlink(&inet_csk(sk)->icsk_accept_queue, req);
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}
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static inline void inet_csk_reqsk_queue_drop(struct sock *sk,
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struct request_sock *req)
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{
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inet_csk_reqsk_queue_unlink(sk, req);
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inet_csk_reqsk_queue_removed(sk, req);
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reqsk_put(req);
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}
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void inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req);
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void inet_csk_destroy_sock(struct sock *sk);
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void inet_csk_prepare_forced_close(struct sock *sk);
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@ -212,24 +212,6 @@ static inline int reqsk_queue_empty(struct request_sock_queue *queue)
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return queue->rskq_accept_head == NULL;
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}
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static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
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struct request_sock *req)
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{
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struct listen_sock *lopt = queue->listen_opt;
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struct request_sock **prev;
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spin_lock(&queue->syn_wait_lock);
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prev = &lopt->syn_table[req->rsk_hash];
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while (*prev != req)
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prev = &(*prev)->dl_next;
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*prev = req->dl_next;
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spin_unlock(&queue->syn_wait_lock);
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if (del_timer(&req->rsk_timer))
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reqsk_put(req);
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}
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static inline void reqsk_queue_add(struct request_sock_queue *queue,
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struct request_sock *req,
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struct sock *parent,
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@ -453,6 +453,7 @@ static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
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iph->saddr, iph->daddr);
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if (req) {
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nsk = dccp_check_req(sk, skb, req);
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if (!nsk)
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reqsk_put(req);
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return nsk;
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}
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@ -301,6 +301,7 @@ static struct sock *dccp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)
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&iph->daddr, inet6_iif(skb));
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if (req) {
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nsk = dccp_check_req(sk, skb, req);
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if (!nsk)
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reqsk_put(req);
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return nsk;
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}
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@ -186,8 +186,7 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
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if (child == NULL)
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goto listen_overflow;
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inet_csk_reqsk_queue_unlink(sk, req);
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inet_csk_reqsk_queue_removed(sk, req);
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inet_csk_reqsk_queue_drop(sk, req);
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inet_csk_reqsk_queue_add(sk, req, child);
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out:
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return child;
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@ -564,6 +564,40 @@ int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req)
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}
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EXPORT_SYMBOL(inet_rtx_syn_ack);
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/* return true if req was found in the syn_table[] */
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static bool reqsk_queue_unlink(struct request_sock_queue *queue,
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struct request_sock *req)
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{
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struct listen_sock *lopt = queue->listen_opt;
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struct request_sock **prev;
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bool found = false;
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spin_lock(&queue->syn_wait_lock);
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for (prev = &lopt->syn_table[req->rsk_hash]; *prev != NULL;
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prev = &(*prev)->dl_next) {
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if (*prev == req) {
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*prev = req->dl_next;
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found = true;
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break;
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}
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}
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spin_unlock(&queue->syn_wait_lock);
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if (del_timer(&req->rsk_timer))
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reqsk_put(req);
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return found;
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}
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void inet_csk_reqsk_queue_drop(struct sock *sk, struct request_sock *req)
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{
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if (reqsk_queue_unlink(&inet_csk(sk)->icsk_accept_queue, req)) {
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reqsk_queue_removed(&inet_csk(sk)->icsk_accept_queue, req);
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reqsk_put(req);
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}
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}
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EXPORT_SYMBOL(inet_csk_reqsk_queue_drop);
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static void reqsk_timer_handler(unsigned long data)
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{
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struct request_sock *req = (struct request_sock *)data;
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@ -1348,6 +1348,7 @@ static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
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req = inet_csk_search_req(sk, th->source, iph->saddr, iph->daddr);
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if (req) {
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nsk = tcp_check_req(sk, skb, req, false);
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if (!nsk)
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reqsk_put(req);
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return nsk;
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}
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@ -755,10 +755,11 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
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if (!child)
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goto listen_overflow;
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inet_csk_reqsk_queue_unlink(sk, req);
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inet_csk_reqsk_queue_removed(sk, req);
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inet_csk_reqsk_queue_drop(sk, req);
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inet_csk_reqsk_queue_add(sk, req, child);
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/* Warning: caller must not call reqsk_put(req);
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* child stole last reference on it.
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*/
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return child;
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listen_overflow:
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@ -946,6 +946,7 @@ static struct sock *tcp_v6_hnd_req(struct sock *sk, struct sk_buff *skb)
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&ipv6_hdr(skb)->daddr, tcp_v6_iif(skb));
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if (req) {
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nsk = tcp_check_req(sk, skb, req, false);
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if (!nsk)
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reqsk_put(req);
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return nsk;
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}
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