From 581409dacc9176b0de1f6c4ca8d66e13aa8e1b29 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Sat, 10 Jun 2017 14:48:14 +0800 Subject: 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: 626d16f50f39 ("sctp: export some apis or variables for sctp_diag and reuse some for proc") Reported-by: Xiumei Mu Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller --- net/sctp/socket.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/sctp/socket.c') diff --git a/net/sctp/socket.c b/net/sctp/socket.c index f16c8d97b7f3..30aa0a529215 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; -- cgit From 988c7322116970696211e902b468aefec95b6ec4 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Thu, 15 Jun 2017 17:49:08 +0800 Subject: sctp: return next obj by passing pos + 1 into sctp_transport_get_idx In sctp_for_each_transport, pos is used to save how many objs it has dumped. Now it gets the last obj by sctp_transport_get_idx, then gets the next obj by sctp_transport_get_next. The issue is that in the meanwhile if some objs in transport hashtable are removed and the objs nums are less than pos, sctp_transport_get_idx would return NULL and hti.walker.tbl is NULL as well. At this moment it should stop hti, instead of continue getting the next obj. Or it would cause a NULL pointer dereference in sctp_transport_get_next. This patch is to pass pos + 1 into sctp_transport_get_idx to get the next obj directly, even if pos > objs nums, it would return NULL and stop hti. Fixes: 626d16f50f39 ("sctp: export some apis or variables for sctp_diag and reuse some for proc") Signed-off-by: Xin Long Signed-off-by: David S. Miller --- net/sctp/socket.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'net/sctp/socket.c') diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 30aa0a529215..3a8318e518f1 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -4666,9 +4666,8 @@ int sctp_for_each_transport(int (*cb)(struct sctp_transport *, void *), if (err) return err; - sctp_transport_get_idx(net, &hti, pos); - obj = sctp_transport_get_next(net, &hti); - for (; obj && !IS_ERR(obj); obj = sctp_transport_get_next(net, &hti)) { + obj = sctp_transport_get_idx(net, &hti, pos + 1); + for (; !IS_ERR_OR_NULL(obj); obj = sctp_transport_get_next(net, &hti)) { struct sctp_transport *transport = obj; if (!sctp_transport_hold(transport)) -- cgit