linux-kernel - Re: [PATCH] mtd: fix memory leak

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Date:	Sun, 06 Feb 2011 17:08:19 +0200
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Mathias Krause <minipli@...glemail.com>
Cc:	linux-mtd@...ts.infradead.org,
	David Woodhouse <dwmw2@...radead.org>,
	Joern Engel <joern@...ybastard.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: fix memory leak

On Sun, 2011-01-30 at 18:35 +0100, Mathias Krause wrote:
> On 30.01.2011 at 15:52, Artem Bityutskiy wrote:
> > Hi,
> > 
> > On Sun, 2011-01-30 at 10:31 +0100, Mathias Krause wrote:
> >> diff --git a/drivers/mtd/devices/phram.c b/drivers/mtd/devices/phram.c
> >> index 5239328..8d28fa0 100644
> >> --- a/drivers/mtd/devices/phram.c
> >> +++ b/drivers/mtd/devices/phram.c
> >> @@ -117,6 +117,7 @@ static void unregister_devices(void)
> >> 	list_for_each_entry_safe(this, safe, &phram_list, list) {
> >> 		del_mtd_device(&this->mtd);
> >> 		iounmap(this->mtd.priv);
> >> +		kfree(this->mtd.name);
> >> 		kfree(this);
> >> 	}
> > 
> > Since register_device() did not allocate it, unregister_devices() should
> > not free it.
> 
> I agree with you, the internal API is a little quirky regarding that point. register_device() should strdup() the name and not just blindly use it. But since the memory for name was already allocated via kmalloc() in phram_setup() it seems a little nitpicky to copy it once again in register_device().
> 
> > Hence, I think it is better to free(name) just after
> > calling unregister_devices().
> 
> This is not possible because unregister_devices() unregisters all devices, not just a single instance. Though name must be freed for every object in the list. After unregister_devices() returns the list is empty and no pointer to the memory locations do exist any more. So my patch was the straight forward fix for the memory leak.

OK, I agree, I think this patch is good enough, pushed to l2-mtd-2.6.git
tree, thanks.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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