Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace fix from Eric Biederman: "This fixes a race between put_ucounts and get_ucounts that can cause a use after free. The fix works by simplifying the code and so there is not even a temptation to be clever and play spinlock vs atomic reference games" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: ucount: Remove the atomicity from ucount->count
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commit
304362a8bc
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@ -72,7 +72,7 @@ struct ucounts {
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struct hlist_node node;
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struct user_namespace *ns;
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kuid_t uid;
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atomic_t count;
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int count;
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atomic_t ucount[UCOUNT_COUNTS];
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};
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@ -144,7 +144,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
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new->ns = ns;
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new->uid = uid;
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atomic_set(&new->count, 0);
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new->count = 0;
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spin_lock_irq(&ucounts_lock);
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ucounts = find_ucounts(ns, uid, hashent);
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@ -155,8 +155,10 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
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ucounts = new;
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}
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}
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if (!atomic_add_unless(&ucounts->count, 1, INT_MAX))
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if (ucounts->count == INT_MAX)
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ucounts = NULL;
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else
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ucounts->count += 1;
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spin_unlock_irq(&ucounts_lock);
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return ucounts;
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}
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@ -165,13 +167,15 @@ static void put_ucounts(struct ucounts *ucounts)
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{
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unsigned long flags;
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if (atomic_dec_and_test(&ucounts->count)) {
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spin_lock_irqsave(&ucounts_lock, flags);
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spin_lock_irqsave(&ucounts_lock, flags);
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ucounts->count -= 1;
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if (!ucounts->count)
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hlist_del_init(&ucounts->node);
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spin_unlock_irqrestore(&ucounts_lock, flags);
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else
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ucounts = NULL;
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spin_unlock_irqrestore(&ucounts_lock, flags);
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kfree(ucounts);
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}
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kfree(ucounts);
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}
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static inline bool atomic_inc_below(atomic_t *v, int u)
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