From: James Morris <james.morris@microsoft.com>
Date: Wed, 16 Jan 2019 23:41:11 +0000 (-0800)
Subject: LSM: Check for NULL cred-security on free
X-Git-Tag: v4.14.95~21
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b9f9379336425ebd0c07d454857ddbc6fe750b36;p=thirdparty%2Fkernel%2Fstable.git

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 95a1a0f52880c..4fbe4e495c021 100644
--- a/security/security.c
+++ b/security/security.c
@@ -993,6 +993,13 @@ 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);
 }