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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-01-24 12:21:51 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-01-24 12:21:51 -0800 |
| commit | 19ca2c8fecb1592d623fe5e82d6796f8d446268d (patch) | |
| tree | 0756e115d125846f46b302085307768f069434a1 /kernel | |
| parent | a4685d2f58e2230d4e27fb2ee581d7ea35e5d046 (diff) | |
| parent | 880a38547ff08715ce4f1daf9a4bb30c87676e68 (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.c | 14 |
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); } |