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sashalevindhowells
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KEYS: close race between key lookup and freeing
When a key is being garbage collected, it's key->user would get put before the ->destroy() callback is called, where the key is removed from it's respective tracking structures. This leaves a key hanging in a semi-invalid state which leaves a window open for a different task to try an access key->user. An example is find_keyring_by_name() which would dereference key->user for a key that is in the process of being garbage collected (where key->user was freed but ->destroy() wasn't called yet - so it's still present in the linked list). This would cause either a panic, or corrupt memory. Fixes CVE-2014-9529. Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: David Howells <dhowells@redhat.com>
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Diff for: security/keys/gc.c

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Original file line numberDiff line numberDiff line change
@@ -148,12 +148,12 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
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if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
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atomic_dec(&key->user->nikeys);
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key_user_put(key->user);
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/* now throw away the key memory */
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if (key->type->destroy)
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key->type->destroy(key);
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key_user_put(key->user);
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kfree(key->description);
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#ifdef KEY_DEBUGGING

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