linux-kernel - Re: [PATCH 3/5] usb: gadget: f_mass_storage: Prevent NULL pointer dereference

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Date:	Tue, 05 Apr 2011 17:56:47 +0200
From:	"Michal Nazarewicz" <mina86@...a86.com>
To:	gregkh@...e.de, "Roger Quadros" <roger.quadros@...ia.com>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] usb: gadget: f_mass_storage: Prevent NULL pointer
 dereference

On Tue, 05 Apr 2011 17:36:40 +0200, Roger Quadros  
<roger.quadros@...ia.com> wrote:
> Prevent a NULL pointer dereference in fsg_config_from_params() if
> 'file' parameter is not specified.

Have you observed this behaviour?  I don't see how it could happen with
module parameters and if it appears in some gadget it's a bug in the
gadget.  Not that I'm saying checking for null pointer is a bad idea.

> Signed-off-by: Roger Quadros <roger.quadros@...ia.com>
> ---
>  drivers/usb/gadget/f_mass_storage.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/usb/gadget/f_mass_storage.c  
> b/drivers/usb/gadget/f_mass_storage.c
> index 5d7de93..f6bd001 100644
> --- a/drivers/usb/gadget/f_mass_storage.c
> +++ b/drivers/usb/gadget/f_mass_storage.c
> @@ -3177,7 +3177,7 @@ fsg_config_from_params(struct fsg_config *cfg,
>  		lun->removable = /* Removable by default */
>  			params->removable_count <= i || params->removable[i];
>  		lun->filename =
> -			params->file_count > i && params->file[i][0]
> +			params->file_count > i && params->file[i]

You're removing the check if an empty file name has been specified.  It
should read:

+			params->file_count > i && params->file[i] && params->file[i][0]

And since the line is getting pretty long, maybe convert it to a proper
“if”.  I'm sure Greg will like that. ;)

>  			? params->file[i]
>  			: 0;
>  	}

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michal "mina86" Nazarewicz    (o o)
ooo +-----<email/xmpp: mnazarewicz@...gle.com>-----ooO--(_)--Ooo--
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