Commit 581409da authored Jun 10, 2017 by Xin Long Committed by David S. Miller Jun 10, 2017

sctp: disable BH in sctp_for_each_endpoint

Now sctp holds read_lock when foreach sctp_ep_hashtable without disabling
BH. If CPU schedules to another thread A at this moment, the thread A may
be trying to hold the write_lock with disabling BH.

As BH is disabled and CPU cannot schedule back to the thread holding the
read_lock, while the thread A keeps waiting for the read_lock. A dead
lock would be triggered by this.

This patch is to fix this dead lock by calling read_lock_bh instead to
disable BH when holding the read_lock in sctp_for_each_endpoint.

Fixes: 626d16f5 ("sctp: export some apis or variables for sctp_diag and reuse some for proc")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent bf292f1b

net/sctp/socket.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -4622,13 +4622,13 @@ int sctp_for_each_endpoint(int (cb)(struct sctp_endpoint , void *),

		for (head = sctp_ep_hashtable; hash < sctp_ep_hashsize;
		hash++, head++) {
		read_lock(&head->lock);
		read_lock_bh(&head->lock);
		sctp_for_each_hentry(epb, &head->chain) {
		err = cb(sctp_ep(epb), p);
		if (err)
		break;
		}
		read_unlock(&head->lock);
		read_unlock_bh(&head->lock);
		}

		return err;

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