[PATCH AUTOSEL for 4.9 019/293] KEYS: put keyring if install_session_keyring_to_cred() fails

[Sasha Levin]

From: Eric Biggers <ebigg...@google.com>

[ Upstream commit d636bd9f12a66ea3775c9fabbf3f8e118253467a ]

In join_session_keyring(), if install_session_keyring_to_cred() were to
fail, we would leak the keyring reference, just like in the bug fixed by
commit 23567fd052a9 ("KEYS: Fix keyring ref leak in
join_session_keyring()").  Fortunately this cannot happen currently, but
we really should be more careful.  Do this by adding and using a new
error label at which the keyring reference is dropped.

Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: David Howells <dhowe...@redhat.com>
Signed-off-by: James Morris <james.l.mor...@oracle.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 security/keys/process_keys.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 2d35d71d7d9a..88c94e6c2158 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -810,15 +810,14 @@ long join_session_keyring(const char *name)
                ret = PTR_ERR(keyring);
                goto error2;
        } else if (keyring == new->session_keyring) {
-               key_put(keyring);
                ret = 0;
-               goto error2;
+               goto error3;
        }
 
        /* we've got a keyring - now to install it */
        ret = install_session_keyring_to_cred(new, keyring);
        if (ret < 0)
-               goto error2;
+               goto error3;
 
        commit_creds(new);
        mutex_unlock(&key_session_mutex);
@@ -828,6 +827,8 @@ long join_session_keyring(const char *name)
 okay:
        return ret;
 
+error3:
+       key_put(keyring);
 error2:
        mutex_unlock(&key_session_mutex);
 error:
-- 
2.15.1