From: Oliver Neukum <oneukum@suse.com>
To: Jia-Ju Bai <baijiaju1990@gmail.com>,
stern@rowland.harvard.edu, gregkh@linuxfoundation.org
Cc: linux-usb@vger.kernel.org, linux-scsi@vger.kernel.org,
usb-storage@lists.one-eyed-alien.net,
linux-kernel@vger.kernel.org
Subject: Re: [usb-storage] [PATCH] usb: storage: Fix a possible data race in uas_queuecommand_lck
Date: Tue, 08 May 2018 10:27:50 +0200 [thread overview]
Message-ID: <1525768070.24345.8.camel@suse.com> (raw)
In-Reply-To: <20180508074743.13622-1-baijiaju1990@gmail.com>
Am Dienstag, den 08.05.2018, 15:47 +0800 schrieb Jia-Ju Bai:
> The write operations to "cmnd->result" and "cmnd->scsi_done"
> are protected by the lock on line 642-643, but the write operations
> to these data on line 634-635 are not protected by the lock.
> Thus, there may exist a data race for "cmnd->result"
> and "cmnd->scsi_done".
No,
the write operations need no lock. The low level driver at this point
owns the command. We cannot race with abort() for a command within
queuecommand(). We take the lock where we take it to protect
dev->resetting.
I don't see why the scope of the lock would need to be enlarged.
Regards
Oliver
> To fix this data race, the write operations on line 634-635
> should be also protected by the lock.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Nacked-by: Oliver Neukum <oneukum@suse.com>
WARNING: multiple messages have this Message-ID (diff)
From: Oliver Neukum <oneukum@suse.com>
To: Jia-Ju Bai <baijiaju1990@gmail.com>,
stern@rowland.harvard.edu, gregkh@linuxfoundation.org
Cc: linux-usb@vger.kernel.org, linux-scsi@vger.kernel.org,
usb-storage@lists.one-eyed-alien.net,
linux-kernel@vger.kernel.org
Subject: usb: storage: Fix a possible data race in uas_queuecommand_lck
Date: Tue, 08 May 2018 10:27:50 +0200 [thread overview]
Message-ID: <1525768070.24345.8.camel@suse.com> (raw)
Am Dienstag, den 08.05.2018, 15:47 +0800 schrieb Jia-Ju Bai:
> The write operations to "cmnd->result" and "cmnd->scsi_done"
> are protected by the lock on line 642-643, but the write operations
> to these data on line 634-635 are not protected by the lock.
> Thus, there may exist a data race for "cmnd->result"
> and "cmnd->scsi_done".
No,
the write operations need no lock. The low level driver at this point
owns the command. We cannot race with abort() for a command within
queuecommand(). We take the lock where we take it to protect
dev->resetting.
I don't see why the scope of the lock would need to be enlarged.
Regards
Oliver
> To fix this data race, the write operations on line 634-635
> should be also protected by the lock.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Nacked-by: Oliver Neukum <oneukum@suse.com>
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next prev parent reply other threads:[~2018-05-08 8:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-08 7:47 [PATCH] usb: storage: Fix a possible data race in uas_queuecommand_lck Jia-Ju Bai
2018-05-08 7:47 ` Jia-Ju Bai
2018-05-08 8:27 ` Oliver Neukum [this message]
2018-05-08 8:27 ` Oliver Neukum
2018-05-08 8:39 ` [usb-storage] [PATCH] " Jia-Ju Bai
2018-05-08 8:39 ` Jia-Ju Bai
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