linux-kernel - Re: [PATCH] led: simplify led_trigger_register

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]

Date:	Thu, 20 Nov 2008 14:45:59 +0000
From:	Richard Purdie <rpurdie@...ux.intel.com>
To:	felipe.balbi@...ia.com
Cc:	me@...ipebalbi.com, linux-kernel@...r.kernel.org,
	Anton Vorontsov <cbou@...l.ru>,
	David Woodhouse <dwmw2@...radead.org>,
	Greg KH <greg@...ah.com>, Pierre Ossman <drzeus@...eus.cx>
Subject: Re: [PATCH] led: simplify led_trigger_register_simple

On Thu, 2008-11-20 at 16:14 +0200, Felipe Balbi wrote:
> > In answer to your question about kfree, I agree it needs to be called
> > upon error. The callers should just be calling
> > led_trigger_unregister_simple() in their failure paths though which
> > should take care of all problems? I know we used to register the simple
> > triggers late in paths so no error handling was needed to keep the code
> > simple and minimise the LED triggers impact on those systems.
> 
> Well, led_trigger_register_simple() doesn't return anything. Imagine
> led_trigger_register_simple() fails, but the driver author decides
> it's not a failure if, let's say, a led doesn't turn on when we insert
> a mmc card to the slot since it doesn't change functionality.
> 
> Now, imagine the user notes the led is not turning on and decides to
> unload and reload the module to try again. Once again the led doesn't go
> on. If the user keeps trying, it's quite a dangerous memory leak, right
> ?

So we have the module loading and one of two things happens:

led_trigger_register_simple() succeeds
led_trigger_register_simple() fails (probably from kmalloc failure)

The module doesn't know or care which happened. When the module unloads
it calls led_trigger_unregister_simple() which will free the memory in
the success case and do nothing in the case where it had failed.

So there is no memory leak?

Cheers,

Richard

--
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/