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inet: fix race in reqsk_queue_unlink()
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reqsk_timer_handler() tests if icsk_accept_queue.listen_opt
is NULL at its beginning.

By the time it calls inet_csk_reqsk_queue_drop() and
reqsk_queue_unlink(), listener might have been closed and
inet_csk_listen_stop() had called reqsk_queue_yank_acceptq()
which sets icsk_accept_queue.listen_opt to NULL

We therefore need to correctly check listen_opt being NULL
after holding syn_wait_lock for proper synchronization.

Fixes: fa76ce7 ("inet: get rid of central tcp/dccp listener timer")
Fixes: b357a36 ("inet: fix possible panic in reqsk_queue_unlink()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Oct 5, 2015
1 parent 8695a14 commit 2306c70
Showing 1 changed file with 10 additions and 9 deletions.
19 changes: 10 additions & 9 deletions net/ipv4/inet_connection_sock.c
Original file line number Diff line number Diff line change
Expand Up @@ -577,21 +577,22 @@ EXPORT_SYMBOL(inet_rtx_syn_ack);
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;
struct listen_sock *lopt;
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;
lopt = queue->listen_opt;
if (lopt) {
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 (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))
reqsk_put(req);
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