linux-kernel - Re: [PATCH] Staging: rtl8192e: Fix segfault upon alloc failure

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Date:	Wed, 5 Nov 2014 14:56:41 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Daniel Dressler <danieru.dressler@...il.com>
Cc:	Matthew Casey <mdcasey@...bloom.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	"open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Staging: rtl8192e: Fix segfault upon alloc failure

On Thu, Nov 06, 2014 at 01:11:17AM +0900, Daniel Dressler wrote:
> Kernel space allocations can fail. This patch
> fixes a crash condition upon allocation failure.
> 
> Should this condition occur init_firmware() will
> goto its error handler and declare download failure.
> 
> Of interesting note is that prior to this patch
> fw_download_code() could never fail yet our caller
> checked the return value.
> 
> Reported-by: RUC_Soft_Sec <rucsoftsec@...il.com>
> Signed-off-by: Daniel Dressler <danieru.dressler@...il.com>
> ---
>  drivers/staging/rtl8192e/rtl8192e/r8192E_firmware.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/staging/rtl8192e/rtl8192e/r8192E_firmware.c b/drivers/staging/rtl8192e/rtl8192e/r8192E_firmware.c
> index 2e28744..e4257fe 100644
> --- a/drivers/staging/rtl8192e/rtl8192e/r8192E_firmware.c
> +++ b/drivers/staging/rtl8192e/rtl8192e/r8192E_firmware.c
> @@ -61,6 +61,9 @@ static bool fw_download_code(struct net_device *dev, u8 *code_virtual_address,
>  		}
>  
>  		skb  = dev_alloc_skb(frag_length + 4);
> +		if (!skb)
> +			return false;

Lots of people try to fix this "warning" in this manner.  But you have
to do more work here than just a simple "return false;", you need to
unwind all of the work you have done up to this point, which is a
non-trivial task...

I'd recommend looking at how other drivers of this manufacturer handle
this type of operation to get a better idea of how to rewrite this
function.

good luck,

greg k-h
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