linux-kernel - Re: [PATCH] scsi: bsg: Fix device unregistration

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Date:   Sat, 11 Sep 2021 09:41:03 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Johan Hovold <johan@...nel.org>
CC:     <linux-scsi@...r.kernel.org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <fujita.tomonori@....ntt.co.jp>,
        <axboe@...nel.dk>, <martin.petersen@...cle.com>, <hch@....de>,
        <gregkh@...uxfoundation.org>, <wanghaibin.wang@...wei.com>
Subject: Re: [PATCH] scsi: bsg: Fix device unregistration

On 2021/9/10 20:45, Johan Hovold wrote:
> On Thu, Sep 09, 2021 at 11:46:08AM +0800, Zenghui Yu wrote:

>> @@ -218,6 +226,7 @@ struct bsg_device *bsg_register_queue(struct request_queue *q,
>>  out_device_del:
>>  	cdev_device_del(&bd->cdev, &bd->device);
>>  out_ida_remove:
>> +	put_device(&bd->device);
>>  	ida_simple_remove(&bsg_minor_ida, MINOR(bd->device.devt));
>>  out_kfree:
>>  	kfree(bd);
> 
> Ehh, what about the blatant use-after-free and double-free you just
> added here?

Yeah, whoops. That's definitely wrong. I'm squash the following fix
in this patch.

Thanks for the heads up!

|diff --git a/block/bsg.c b/block/bsg.c
|index c3bb92b9af7e..882f56bff14f 100644
|--- a/block/bsg.c
|+++ b/block/bsg.c
|@@ -200,7 +200,8 @@ struct bsg_device *bsg_register_queue(struct 
request_queue *q,
|        if (ret < 0) {
|                if (ret == -ENOSPC)
|                        dev_err(parent, "bsg: too many bsg devices\n");
|-               goto out_kfree;
|+               kfree(bd);
|+               return ERR_PTR(ret);
|        }
|        bd->device.devt = MKDEV(bsg_major, ret);
|        bd->device.class = bsg_class;
|@@ -213,7 +214,7 @@ struct bsg_device *bsg_register_queue(struct 
request_queue *q,
|        bd->cdev.owner = THIS_MODULE;
|        ret = cdev_device_add(&bd->cdev, &bd->device);
|        if (ret)
|-               goto out_ida_remove;
|+               goto out_put_device;
|
|        if (q->kobj.sd) {
|                ret = sysfs_create_link(&q->kobj, &bd->device.kobj, "bsg");
|@@ -225,11 +226,8 @@ struct bsg_device *bsg_register_queue(struct 
request_queue *q,
|
| out_device_del:
|        cdev_device_del(&bd->cdev, &bd->device);
|-out_ida_remove:
|+out_put_device:
|        put_device(&bd->device);
|-       ida_simple_remove(&bsg_minor_ida, MINOR(bd->device.devt));
|-out_kfree:
|-       kfree(bd);
|        return ERR_PTR(ret);
| }
| EXPORT_SYMBOL_GPL(bsg_register_queue);