linux-kernel - Re: [PATCH] USB: gadget: f_mass_storage: fix in fsg_common

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Message-id: <op.vck8y0uv7p4s8u@pikus>
Date:	Wed, 12 May 2010 12:34:02 +0200
From:	Michał Nazarewicz <m.nazarewicz@...sung.com>
To:	Viral Mehta <Viral.Mehta@...infotech.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Cc:	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] USB: gadget: f_mass_storage: fix in fsg_common_init()
 error recovery

On Wed, 12 May 2010 12:06:11 +0200, Viral Mehta <Viral.Mehta@...infotech.com> wrote:
> In fsg_common_release(), we are freeing common->luns.
> 2894         kfree(common->luns);
>
> However, these gets allocd in fsg_common_init()
> 2712         /* Create the LUNs, open their backing files, and register the
> 2713          * LUN devices in sysfs. */
> 2714         curlun = kzalloc(nluns * sizeof *curlun, GFP_KERNEL);
> 2715         if (!curlun) {
> 2716                 kfree(common);
> 2717                 return ERR_PTR(-ENOMEM);
> 2718         }
>
> Now, if this kzalloc at line 2714 failed
> And if your patch is applied, you will follow error_release path which in
> turn will call kfree on a pointer whose allocation is failed.

If luns allocation fails, common->luns will be NULL and freeing a NULL
pointer is a no-operation thus the code works just fine.

-- 
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| Humble Liege of Serenely Enlightened Majesty of  o' \,=./ `o
| Computer Science,  Michał "mina86" Nazarewicz       (o o)
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