linux-kernel - [PATCH -next] scsi: core: fix double free in raid_component

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Date:   Sat, 19 Aug 2023 08:03:45 +0000
From:   Zhu Wang <wangzhu9@...wei.com>
To:     <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>,
        <bvanassche@....org>, <dan.carpenter@...aro.org>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <wangzhu9@...wei.com>
Subject: [PATCH -next] scsi: core: fix double free in raid_component_add()

Previous commit 04b5b5cb0136 ("scsi: core: Fix possible memory leak if
device_add() fails") introduced a double free when device_add() failed.
When device_add() failed, the put_device(&rc->dev) is called, which will
call raid_component_release(), and this function will call
put_device(rc->dev.parent) and kfree(rc), but in the error path of
raid_component_release() above two functions are called again, so 'rc' are
freed twice.

We do not just revert the patch, since the memory allocated by
dev_set_name() is not released in the error path, it should be released
through calling put_device(&rc->dev) which will call kobject_cleanup(),
and the device name will be released in it. Though the commit 04b5b5cb0136
("scsi: core: Fix possible memory leak if device_add() fails") fixed the
memory leak, it didn't consider the double free problem. We removed
put_device(rc->dev.parent) and kfree(rc) in the error path, and we moved
put_device(&rc->dev) after rd->component-count--, since after
put_device(&rc->dev) is called, 'rc' is freed, so list_del(&rc->node)
cannot be called again.

Fixes: 04b5b5cb0136 ("scsi: core: Fix possible memory leak if device_add() fails")
Signed-off-by: Zhu Wang <wangzhu9@...wei.com>
---
 drivers/scsi/raid_class.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/scsi/raid_class.c b/drivers/scsi/raid_class.c
index 711252e52d8e..86ed1f66d749 100644
--- a/drivers/scsi/raid_class.c
+++ b/drivers/scsi/raid_class.c
@@ -248,11 +248,9 @@ int raid_component_add(struct raid_template *r,struct device *raid_dev,
 	return 0;

 err_out:
-	put_device(&rc->dev);
 	list_del(&rc->node);
 	rd->component_count--;
-	put_device(component_dev);
-	kfree(rc);
+	put_device(&rc->dev);
 	return err;
 }
 EXPORT_SYMBOL(raid_component_add);
-- 
2.34.1