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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, Wen Yang <wenyang@linux.alibaba.com>,
        Sudeep Holla <sudeep.holla@arm.com>
Subject: [PATCH 5.4 147/191] firmware: arm_scmi: Avoid double free in error flow
Date:   Tue,  7 Jan 2020 21:54:27 +0100
Message-Id: <20200107205340.839413251@linuxfoundation.org>
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From: Wen Yang <wenyang@linux.alibaba.com>

commit 8305e90a894f82c278c17e51a28459deee78b263 upstream.

If device_register() fails, both put_device() and kfree() are called,
ending with a double free of the scmi_dev.

Calling kfree() is needed only when a failure happens between the
allocation of the scmi_dev and its registration, so move it to there
and remove it from the error flow.

Fixes: 46edb8d1322c ("firmware: arm_scmi: provide the mandatory device release callback")
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/firmware/arm_scmi/bus.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -135,8 +135,10 @@ scmi_device_create(struct device_node *n
 		return NULL;
 
 	id = ida_simple_get(&scmi_bus_id, 1, 0, GFP_KERNEL);
-	if (id < 0)
-		goto free_mem;
+	if (id < 0) {
+		kfree(scmi_dev);
+		return NULL;
+	}
 
 	scmi_dev->id = id;
 	scmi_dev->protocol_id = protocol;
@@ -154,8 +156,6 @@ scmi_device_create(struct device_node *n
 put_dev:
 	put_device(&scmi_dev->dev);
 	ida_simple_remove(&scmi_bus_id, id);
-free_mem:
-	kfree(scmi_dev);
 	return NULL;
 }