linux-kernel - [PATCH] firmware: arm_scmi: avoid double free in error flow

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Message-Id: <20191125155409.9948-1-wenyang@linux.alibaba.com>
Date:   Mon, 25 Nov 2019 23:54:09 +0800
From:   Wen Yang <wenyang@...ux.alibaba.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Wen Yang <wenyang@...ux.alibaba.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] firmware: arm_scmi: avoid double free in error flow

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@...ux.alibaba.com>
Cc: Sudeep Holla <sudeep.holla@....com>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/firmware/arm_scmi/bus.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index 92f843ea..7a30952 100644
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -135,8 +135,10 @@ struct scmi_device *
 		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 @@ struct scmi_device *
 put_dev:
 	put_device(&scmi_dev->dev);
 	ida_simple_remove(&scmi_bus_id, id);
-free_mem:
-	kfree(scmi_dev);
 	return NULL;
 }
 
-- 
1.8.3.1