linux-kernel - Re: [PATCH] drivers/net/wimax/i2400m/fw.c fix possible double free

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Date:	Tue, 16 Mar 2010 23:05:47 -0700
From:	Inaky Perez-Gonzalez <inaky@...ux.intel.com>
To:	David Miller <davem@...emloft.net>
Cc:	darrenrjenkins@...il.com, cindy.h.kao@...el.com,
	wimax@...uxwimax.org, netdev@...r.kernel.org,
	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-wimax@...el.com
Subject: Re: [PATCH] drivers/net/wimax/i2400m/fw.c fix possible double free

On Tue, 2010-03-16 at 14:14 -0700, David Miller wrote: 
> From: Darren Jenkins <darrenrjenkins@...il.com>
> Date: Tue, 16 Mar 2010 22:46:28 +1100
> 
> > i2400m_fw_check() can free i2400m->fw_hdrs if krealloc() fails causing a double free
> > Add a check so we don't free the memory a second time.
> > 
> > coverity CID: 13455
> > 
> > Signed-off-by: Darren Jenkins <darrenrjenkins@...il.com>
> 
> Please don't fix it like this, the check is obscure and it's
> allowing other bugs to happen.
> 
> If krealloc() fails, any refrence to i2400m->fw_hdrs is
> referencing freed memory.
> 
> Therefore the krealloc() failure handling in this driver should NULL
> out i2400m->fw_hdrs and that will fix the double kfree problem as well
> as trap any stray references.

I agree with David, the fix is quite obscure. The error path in
i2400m_fw_check()'s call to i2400m_kzrealloc_2x() should be rather
cleaning up in a better way.






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