2015-02-11 21:26:59

by David Jeffery

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

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 <[email protected]>

---

The basic way to trigger this is to use keyctl to revoke a session's keyring,
then do an action which will trigger request_key(). request_key() will fail
and a key will leak.


diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 0c7aea4..486ef6f 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -414,6 +414,7 @@ link_check_failed:

link_prealloc_failed:
mutex_unlock(&user->cons_lock);
+ key_put(key);
kleave(" = %d [prelink]", ret);
return ret;

2015-02-12 16:46:20

by David Howells

Subject: Re: [PATCH] Don't leak a key reference if request_key() tries to use a revoked keyring

David Jeffery <[email protected]> wrote:

> 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.

Applied.