[PATCH for 3.18] Don't leak a key reference if request_key() tries to use a revoked keyring

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From: David Jeffery <djeffery@xxxxxxxxxx>

commit d0709f1e66e8066c4ac6a54620ec116aa41937c0 upstream.
[Please apply to 3.18-stable.]

If a request_key() call to allocate and fill out a key attempts to insert the
key structure into a revoked keyring, the key will leak, using memory and part
of the user's key quota until the system reboots. This is from a failure of
construct_alloc_key() to decrement the key's reference count after the attempt
to insert into the requested keyring is rejected.

key_put() needs to be called in the link_prealloc_failed callpath to ensure
the unused key is released.

Signed-off-by: David Jeffery <djeffery@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
 security/keys/request_key.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 8117a774ee5d..edc367ef0bd6 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -437,6 +437,7 @@ link_check_failed:
 
 link_prealloc_failed:
 	mutex_unlock(&user->cons_lock);
+	key_put(key);
 	kleave(" = %d [prelink]", ret);
 	return ret;
 
-- 
2.15.1.504.g5279b80103-goog




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