linux-kernel - Re: [PATCH] gpiolib: Fix locking on gpio debugfs files

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] [day] [month] [year] [list]

Date:	Tue, 12 Feb 2013 11:27:54 +0900
From:	Alexandre Courbot <acourbot@...dia.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH] gpiolib: Fix locking on gpio debugfs files

On Mon, Feb 11, 2013 at 8:31 PM, Grant Likely <grant.likely@...retlab.ca> wrote:
> On Mon, Feb 11, 2013 at 4:28 AM, Alex Courbot <acourbot@...dia.com> wrote:
>> Just wondering: if we manage to change this spinlock into a mutex in the
>> future, wouldn't it be better to acquire it only once in gpiolib_seq_start()
>> and release it in gpiolib_seq_stop()?
>>
>> Even though the protection introduced by this patch definitely improves the
>> situation, it seems to me that chips could still be removed while being
>> displayed by gpiolib_seq_show().
>
> Probably, but need to first verify that the mutex won't end up getting
> held between read() syscalls. Otherwise it would be possible to block
> addition/removal by holding the file open. I cursory read of seq_file
> looks like ->stop() is always called, but I would appreciate someone
> more cluefull to give an opinion here.

While not cluefull in any way, I nonetheless had a quick look at all
the control paths of seq_read(), and indeed op->stop() seems to be
called in each of them.

> I've also got a draft patch that turns gpio chips into first-class
> kobjects which means we can do proper reference counting on them and
> prevent the structure from actually disappearing while other drivers
> still hold references.

Oooh. Looking forward to seeing this. :)

Alex.
--
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/