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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,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Arun Kumar Neelakantam <aneela@codeaurora.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>
Subject: [PATCH 4.19 26/47] rpmsg: glink: Fix use after free in open_ack TIMEOUT case
Date:   Thu, 19 Dec 2019 19:34:40 +0100
Message-Id: <20191219182931.586960513@linuxfoundation.org>
In-Reply-To: <20191219182857.659088743@linuxfoundation.org>
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From: Arun Kumar Neelakantam <aneela@codeaurora.org>

commit ac74ea01860170699fb3b6ea80c0476774c8e94f upstream.

Extra channel reference put when remote sending OPEN_ACK after timeout
causes use-after-free while handling next remote CLOSE command.

Remove extra reference put in timeout case to avoid use-after-free.

Fixes: b4f8e52b89f6 ("rpmsg: Introduce Qualcomm RPM glink driver")
Cc: stable@vger.kernel.org
Tested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/rpmsg/qcom_glink_native.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/rpmsg/qcom_glink_native.c
+++ b/drivers/rpmsg/qcom_glink_native.c
@@ -1106,13 +1106,12 @@ static int qcom_glink_create_remote(stru
 close_link:
 	/*
 	 * Send a close request to "undo" our open-ack. The close-ack will
-	 * release the last reference.
+	 * release qcom_glink_send_open_req() reference and the last reference
+	 * will be relesed after receiving remote_close or transport unregister
+	 * by calling qcom_glink_native_remove().
 	 */
 	qcom_glink_send_close_req(glink, channel);
 
-	/* Release qcom_glink_send_open_req() reference */
-	kref_put(&channel->refcount, qcom_glink_channel_release);
-
 	return ret;
 }