[PATCH] ocfs2: cluster: fix potential deadlodddck on &o2net_debug_lock

[Chengfeng Ye]

&o2net_debug_lock is acquired by timer o2net_idle_timer() along the
following call chain. Thus the acquisition of the lock under process
context should disable bottom half, otherwise deadlock could happen
if the timer happens to preempt the execution while the lock is held
in process context on the same CPU.

<timer interrupt>
        -> o2net_idle_timer()
        -> queue_delayed_work()
        -> sc_put()
        -> sc_kref_release()
        -> o2net_debug_del_sc()
        -> spin_lock(&o2net_debug_lock);

Several lock acquisition of &o2net_debug_lock under process context
do not disable irq or bottom half. The patch fixes these potential
deadlocks scenerio by using spin_lock_bh() on &o2net_debug_lock.

This flaw was found by an experimental static analysis tool I am
developing for irq-related deadlock. x86_64 allmodconfig using gcc
shows no new warning.

Signed-off-by: Chengfeng Ye <dg573847474@xxxxxxxxx>
---
 fs/ocfs2/cluster/netdebug.c | 40 ++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/fs/ocfs2/cluster/netdebug.c b/fs/ocfs2/cluster/netdebug.c
index 35c05c18de59..bc27301eab6d 100644
--- a/fs/ocfs2/cluster/netdebug.c
+++ b/fs/ocfs2/cluster/netdebug.c
@@ -44,17 +44,17 @@ static LIST_HEAD(send_tracking);
 
 void o2net_debug_add_nst(struct o2net_send_tracking *nst)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	list_add(&nst->st_net_debug_item, &send_tracking);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 void o2net_debug_del_nst(struct o2net_send_tracking *nst)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	if (!list_empty(&nst->st_net_debug_item))
 		list_del_init(&nst->st_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 static struct o2net_send_tracking
@@ -84,9 +84,9 @@ static void *nst_seq_start(struct seq_file *seq, loff_t *pos)
 {
 	struct o2net_send_tracking *nst, *dummy_nst = seq->private;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	nst = next_nst(dummy_nst);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return nst;
 }
@@ -95,13 +95,13 @@ static void *nst_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
 	struct o2net_send_tracking *nst, *dummy_nst = seq->private;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	nst = next_nst(dummy_nst);
 	list_del_init(&dummy_nst->st_net_debug_item);
 	if (nst)
 		list_add(&dummy_nst->st_net_debug_item,
 			 &nst->st_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return nst; /* unused, just needs to be null when done */
 }
@@ -112,7 +112,7 @@ static int nst_seq_show(struct seq_file *seq, void *v)
 	ktime_t now;
 	s64 sock, send, status;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	nst = next_nst(dummy_nst);
 	if (!nst)
 		goto out;
@@ -145,7 +145,7 @@ static int nst_seq_show(struct seq_file *seq, void *v)
 		   (long long)status);
 
 out:
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return 0;
 }
@@ -191,16 +191,16 @@ static const struct file_operations nst_seq_fops = {
 
 void o2net_debug_add_sc(struct o2net_sock_container *sc)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	list_add(&sc->sc_net_debug_item, &sock_containers);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 void o2net_debug_del_sc(struct o2net_sock_container *sc)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	list_del_init(&sc->sc_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 struct o2net_sock_debug {
@@ -236,9 +236,9 @@ static void *sc_seq_start(struct seq_file *seq, loff_t *pos)
 	struct o2net_sock_debug *sd = seq->private;
 	struct o2net_sock_container *sc, *dummy_sc = sd->dbg_sock;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	sc = next_sc(dummy_sc);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return sc;
 }
@@ -248,12 +248,12 @@ static void *sc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 	struct o2net_sock_debug *sd = seq->private;
 	struct o2net_sock_container *sc, *dummy_sc = sd->dbg_sock;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	sc = next_sc(dummy_sc);
 	list_del_init(&dummy_sc->sc_net_debug_item);
 	if (sc)
 		list_add(&dummy_sc->sc_net_debug_item, &sc->sc_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return sc; /* unused, just needs to be null when done */
 }
@@ -349,7 +349,7 @@ static int sc_seq_show(struct seq_file *seq, void *v)
 	struct o2net_sock_debug *sd = seq->private;
 	struct o2net_sock_container *sc, *dummy_sc = sd->dbg_sock;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	sc = next_sc(dummy_sc);
 
 	if (sc) {
@@ -359,7 +359,7 @@ static int sc_seq_show(struct seq_file *seq, void *v)
 			sc_show_sock_stats(seq, sc);
 	}
 
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return 0;
 }
-- 
2.17.1