linux-kernel - Re: [PATCH 1/2] scsi: sr: Fix sr_probe() missing mutex

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Date:   Sat, 30 May 2020 11:14:51 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     jejb@...ux.ibm.com, Simon Arlott <simon@...iron.net>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     linux-scsi@...r.kernel.org, Merlijn Wajer <merlijn@...hive.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] scsi: sr: Fix sr_probe() missing mutex_destroy

On 2020-05-30 09:41, James Bottomley wrote:
> On Sat, 2020-05-30 at 09:24 -0700, Bart Van Assche wrote:
>> On 2020-05-30 02:32, Simon Arlott wrote:
>>> If the device minor cannot be allocated or the cdrom fails to be
>>> registered then the mutex should be destroyed.
>>
>> Please add Fixes: and Cc: stable tags.
> 
> This isn't really a bug, is it?  mutex_destroy is a nop unless lock
> debugging is enabled in which case it checks the lock is unlocked and
> marks it as unusable to detect a use after destroy.  Since the
> structure containing the mutex is kfree'd in the next statement, kasan
> would also detect any use after free.  That's not to say we shouldn't
> do this to be fully correct ... just that it has no potential ever to
> have user visible impact so there doesn't seem to be much point
> cluttering up the stable process with it.

That makes sense to me. I may have confused Simon with my suggestion.

Bart.