LSM: Check for NULL cred-security on free

commit a5795fd38ee8194451ba3f281f075301a3696ce2 upstream.

From: Casey Schaufler <casey@schaufler-ca.com>

Check that the cred security blob has been set before trying
to clean it up. There is a case during credential initialization
that could result in this.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
Reported-by: syzbot+69ca07954461f189e808@syzkaller.appspotmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/security.c b/security/security.c
index 46f405c..0dde287 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -861,6 +861,13 @@ int security_cred_alloc_blank(struct cred *cred, gfp_t gfp)
 
 void security_cred_free(struct cred *cred)
 {
+       /*
+        * There is a failure case in prepare_creds() that
+        * may result in a call here with ->security being NULL.
+        */
+       if (unlikely(cred->security == NULL))
+               return;
+
        call_void_hook(cred_free, cred);
 }