[PATCH net] sctp: disable BH in sctp_for_each_endpoint

[Xin Long]

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 <x...@redhat.com>
Signed-off-by: Xin Long <lucien....@gmail.com>
---
 net/sctp/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index f16c8d9..30aa0a5 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -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;
-- 
2.1.0