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authorLinus Torvalds <torvalds@linux-foundation.org>2017-01-24 12:21:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-24 12:21:51 -0800
commit19ca2c8fecb1592d623fe5e82d6796f8d446268d (patch)
tree0756e115d125846f46b302085307768f069434a1 /kernel
parenta4685d2f58e2230d4e27fb2ee581d7ea35e5d046 (diff)
parent880a38547ff08715ce4f1daf9a4bb30c87676e68 (diff)
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace fix from Eric Biederman: "This has a single brown bag fix. The possible deadlock with dec_pid_namespaces that I had thought was fixed earlier turned out only to have been moved. So instead of being cleaver this change takes ucounts_lock with irqs disabled. So dec_ucount can be used from any context without fear of deadlock. The items accounted for dec_ucount and inc_ucount are all comparatively heavy weight objects so I don't exepct this will have any measurable performance impact" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: userns: Make ucounts lock irq-safe
Diffstat (limited to 'kernel')
-rw-r--r--kernel/ucount.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 9d20d5dd298a..4bbd38ec3788 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -128,10 +128,10 @@ 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_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent);
if (!ucounts) {
- spin_unlock(&ucounts_lock);
+ spin_unlock_irq(&ucounts_lock);
new = kzalloc(sizeof(*new), GFP_KERNEL);
if (!new)
@@ -141,7 +141,7 @@ 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_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent);
if (ucounts) {
kfree(new);
@@ -152,16 +152,18 @@ 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_irq(&ucounts_lock);
return ucounts;
}
static void put_ucounts(struct ucounts *ucounts)
{
+ unsigned long flags;
+
if (atomic_dec_and_test(&ucounts->count)) {
- spin_lock(&ucounts_lock);
+ spin_lock_irqsave(&ucounts_lock, flags);
hlist_del_init(&ucounts->node);
- spin_unlock(&ucounts_lock);
+ spin_unlock_irqrestore(&ucounts_lock, flags);
kfree(ucounts);
}