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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Tom Rix <trix@redhat.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.16 117/227] mctp: fix use after free
Date:   Mon, 21 Feb 2022 09:48:56 +0100
Message-Id: <20220221084938.753002243@linuxfoundation.org>
In-Reply-To: <20220221084934.836145070@linuxfoundation.org>
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From: Tom Rix <trix@redhat.com>

commit 7e5b6a5c8c44310784c88c1c198dde79f6402f7b upstream.

Clang static analysis reports this problem
route.c:425:4: warning: Use of memory after it is freed
  trace_mctp_key_acquire(key);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
When mctp_key_add() fails, key is freed but then is later
used in trace_mctp_key_acquire().  Add an else statement
to use the key only when mctp_key_add() is successful.

Fixes: 4f9e1ba6de45 ("mctp: Add tracepoints for tag/key handling")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mctp/route.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -414,13 +414,14 @@ static int mctp_route_input(struct mctp_
 			 * this function.
 			 */
 			rc = mctp_key_add(key, msk);
-			if (rc)
+			if (rc) {
 				kfree(key);
+			} else {
+				trace_mctp_key_acquire(key);
 
-			trace_mctp_key_acquire(key);
-
-			/* we don't need to release key->lock on exit */
-			mctp_key_unref(key);
+				/* we don't need to release key->lock on exit */
+				mctp_key_unref(key);
+			}
 			key = NULL;
 
 		} else {