linux-kernel - [PATCH] scsi: sd: call device_del() if device_add

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Message-Id: <20220329154948.10350-1-fmdefrancesco@gmail.com>
Date:   Tue, 29 Mar 2022 17:49:48 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        syzbot+f08c77040fa163a75a46@...kaller.appspotmail.com
Subject: [PATCH] scsi: sd: call device_del() if device_add_disk() fails

In sd_probe(), if device_add_disk() fails it simply calls put_device()
and jumps to the "out" label but the device is never deleted from system.
This leads to a memory leak as reported by Syzbot.[1]

Fix this bug by calling device_del() soon before put_device() when 
device_add_disk() fails.

[1] [syzbot] memory leak in blk_mq_init_tags
https://lore.kernel.org/lkml/000000000000c341cc05db38c1b0@google.com/

Reported-by: syzbot+f08c77040fa163a75a46@...kaller.appspotmail.com
Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
Fixes: 2a7a891f4c40 ("scsi: sd: Add error handling support for add_disk()")
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
---

This patch replace the previous attempt to fix the bug reported by
Syzbot. Therefore, the previous wrong patch at 
https://lore.kernel.org/lkml/20220328084452.11479-1-fmdefrancesco@gmail.com/
must be discarded.

Many thanks to Dan Carpenter.

 drivers/scsi/sd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index a390679cf458..13d96d0f9dde 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3474,6 +3474,7 @@ static int sd_probe(struct device *dev)
 
 	error = device_add_disk(dev, gd, NULL);
 	if (error) {
+		device_del(&sdkp->disk_dev);
 		put_device(&sdkp->disk_dev);
 		goto out;
 	}
-- 
2.34.1