[PATCH] userns: Make ucounts lock softirq-safe

[Nikolay Borisov]

The ucounts_lock is being used to protect various ucounts lifecycle
management functionalities. However, those services can also be invoked
when a pidns is being freed in an RCU callback (e.g. softirq context).
This can lead to deadlocks. Fix it by making the spinlock disable softirq

Signed-off-by: Nikolay Borisov <n.borisov.lkml@xxxxxxxxx>
---
 kernel/ucount.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/ucount.c b/kernel/ucount.c
index b4aaee935b3e..23a44ea894cd 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -132,10 +132,10 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
 	struct hlist_head *hashent = ucounts_hashentry(ns, uid);
 	struct ucounts *ucounts, *new;
 
-	spin_lock(&ucounts_lock);
+	spin_lock_bh(&ucounts_lock);
 	ucounts = find_ucounts(ns, uid, hashent);
 	if (!ucounts) {
-		spin_unlock(&ucounts_lock);
+		spin_unlock_bh(&ucounts_lock);
 
 		new = kzalloc(sizeof(*new), GFP_KERNEL);
 		if (!new)
@@ -145,7 +145,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
 		new->uid = uid;
 		atomic_set(&new->count, 0);
 
-		spin_lock(&ucounts_lock);
+		spin_lock_bh(&ucounts_lock);
 		ucounts = find_ucounts(ns, uid, hashent);
 		if (ucounts) {
 			kfree(new);
@@ -156,16 +156,16 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
 	}
 	if (!atomic_add_unless(&ucounts->count, 1, INT_MAX))
 		ucounts = NULL;
-	spin_unlock(&ucounts_lock);
+	spin_unlock_bh(&ucounts_lock);
 	return ucounts;
 }
 
 static void put_ucounts(struct ucounts *ucounts)
 {
 	if (atomic_dec_and_test(&ucounts->count)) {
-		spin_lock(&ucounts_lock);
+		spin_lock_bh(&ucounts_lock);
 		hlist_del_init(&ucounts->node);
-		spin_unlock(&ucounts_lock);
+		spin_unlock_bh(&ucounts_lock);
 
 		kfree(ucounts);
 	}
-- 
2.7.4


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