[PATCH 4.11 11/84] sctp: disable BH in sctp_for_each_endpoint

Greg Kroah-Hartman
2017-07-03T13:47:12Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 581409dacc9176b0de1f6c4ca8d66e13aa8e1b29 ]

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: 626d16f50f39 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/socket.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4586,13 +4586,13 @@ int sctp_for_each_endpoint(int (*cb)(str

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;