[PATCH] KEYS: fix key refcount leak in keyctl_assume_authority()

Eric Biggers ebiggers3 at gmail.com
Mon Sep 18 18:36:12 UTC 2017

From: Eric Biggers <ebiggers at google.com>

In keyctl_assume_authority(), if keyctl_change_reqkey_auth() were to
fail, we would leak the reference to the 'authkey'.  Currently this can
only happen if prepare_creds() fails to allocate memory.  But it still
should be fixed, as it is a more severe bug waiting to happen.

This patch also moves the read of 'authkey->serial' to before the
reference to the authkey is dropped.  Doing the read after dropping the
reference is very fragile because it assumes we still hold another
reference to the key.  (Which we do, in current->cred->request_key_auth,
but there's no reason not to write it in the "obviously correct" way.)

Fixes: d84f4f992cbd ("CRED: Inaugurate COW credentials")
Signed-off-by: Eric Biggers <ebiggers at google.com>
 security/keys/keyctl.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 6a82090c7fc1..552e4460683b 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1411,11 +1411,9 @@ long keyctl_assume_authority(key_serial_t id)
 	ret = keyctl_change_reqkey_auth(authkey);
-	if (ret < 0)
-		goto error;
+	if (ret == 0)
+		ret = authkey->serial;
-	ret = authkey->serial;
 	return ret;

To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

More information about the Linux-security-module-archive mailing list