linux-kernel - Re: [PATCHv2 1/1] SCSI: update hosts module to use idr index management

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56157F49.5030101@suse.com>
Date:	Wed, 7 Oct 2015 22:23:37 +0200
From:	Hannes Reinecke <hare@...e.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Lee Duncan <lduncan@...e.com>
Cc:	Christoph Hellwig <hch@...radead.org>, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Johannes Thumshirn <jthumshirn@...e.de>
Subject: Re: [PATCHv2 1/1] SCSI: update hosts module to use idr index
 management

On 10/06/2015 07:17 PM, James Bottomley wrote:
> On Tue, 2015-10-06 at 10:14 -0700, Lee Duncan wrote:
>> On 10/06/2015 02:40 AM, Christoph Hellwig wrote:
>>>>   struct Scsi_Host *scsi_host_lookup(unsigned short hostnum)
>>>>   {
>>>> -	struct device *cdev;
>>>> -	struct Scsi_Host *shost = NULL;
>>>> -
>>>> -	cdev = class_find_device(&shost_class, NULL, &hostnum,
>>>> -				 __scsi_host_match);
>>>> -	if (cdev) {
>>>> -		shost = scsi_host_get(class_to_shost(cdev));
>>>> -		put_device(cdev);
>>>> -	}
>>>> +	struct Scsi_Host *shost;
>>>> +
>>>> +	spin_lock(&host_index_lock);
>>>> +	shost = idr_find(&host_index_idr, hostnum);
>>>> +	spin_unlock(&host_index_lock);
>>>> +
>>>>   	return shost;
>>>
>>> How does this actually grab a reference to the host?
>>
>> Good catch -- I should have noticed that.
>>
>> I will resubmit the patch.
>
> I'll wait to see what you produce, but I don't think, using a separate
> idr array, you can close the race window between lookup and get.  One of
> the nice things about using the cdev iterator is that the get is part of
> the lookup process.
>
Hmm. Should be possible if you free up the IDR in scsi_remove_host(), 
just after setting the state to SHOST_DEL.

Cheers,

Hannes

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/