netdev - Re: [ethtool PATCH] ethtool: Resolve use of uninitialized memory in rxclass_get_dev

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Date:	Mon, 16 Jul 2012 21:03:37 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
CC:	<netdev@...r.kernel.org>, <jeffrey.t.kirsher@...el.com>
Subject: Re: [ethtool PATCH] ethtool: Resolve use of uninitialized memory in
 rxclass_get_dev_info

On Fri, 2012-07-13 at 09:55 -0700, Alexander Duyck wrote:
> The ethtool function for getting the rule count was not zeroing out the
> data field before passing it to the kernel.  As a result the value started
> uninitialized and was incorrectly returning a result indicating that
> devices supported setting new rule indexes.  In order to correct this I am
> adding a one line fix that sets data to zero before we pass the command to
> the kernel.

Right.  For 'get' commands with no parameters (besides the device) the
data copied back to userland is normally zero-initialised and then
filled out by the driver, and I seem to have worked on that assumption.
But because of the odd multiplexing of RX NFC commands
ETHTOOL_GRXCLSRLCNT doesn't work like that.  And for 'my' driver that
didn't matter.  Sorry about that.

(We should really have some explicit documentation of responsibility for
structure initialisation.)

> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
> ---
> 
> I am resending this since I didn't see any notification that it had been seen.
> I also realized that I had not clearly identified that this is an ethtool user
> space patch and not an ethtool kernel space patch.

It was perfectly clear and I had queued it up to review but hadn't yet
done so.

Ben.

>  rxclass.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/rxclass.c b/rxclass.c
> index 4d49aa6..e1633a8 100644
> --- a/rxclass.c
> +++ b/rxclass.c
> @@ -207,6 +207,7 @@ static int rxclass_get_dev_info(struct cmd_context *ctx, __u32 *count,
>  	int err;
>  
>  	nfccmd.cmd = ETHTOOL_GRXCLSRLCNT;
> +	nfccmd.data = 0;
>  	err = send_ioctl(ctx, &nfccmd);
>  	*count = nfccmd.rule_cnt;
>  	if (driver_select)
> 

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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