netdev - Re: [PATCH] net: mwifiex: fix a NULL pointer dereference

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Message-ID: <20190311172419.GA133390@google.com>
Date:   Mon, 11 Mar 2019 10:24:21 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Kangjie Lu <kjlu@....edu>
Cc:     pakki001@....edu, Amitkumar Karwar <amitkarwar@...il.com>,
        Nishant Sarmukadam <nishants@...vell.com>,
        Ganapathi Bhat <gbhat@...vell.com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: mwifiex: fix a NULL pointer dereference

On Mon, Mar 11, 2019 at 02:43:47AM -0500, Kangjie Lu wrote:
> In case dev_alloc_skb fails, the fix returns -ENOMEM to avoid
> NULL pointer dereference.
> 
> Signed-off-by: Kangjie Lu <kjlu@....edu>
> ---
>  drivers/net/wireless/marvell/mwifiex/cmdevt.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/wireless/marvell/mwifiex/cmdevt.c b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
> index 60db2b969e20..5565f18039ab 100644
> --- a/drivers/net/wireless/marvell/mwifiex/cmdevt.c
> +++ b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
> @@ -341,6 +341,12 @@ static int mwifiex_dnld_sleep_confirm_cmd(struct mwifiex_adapter *adapter)
>  		sleep_cfm_tmp =
>  			dev_alloc_skb(sizeof(struct mwifiex_opt_sleep_confirm)
>  				      + MWIFIEX_TYPE_LEN);
> +		if (!sleep_cfm_tmp) {
> +			mwifiex_dbg(adapter, ERROR, 

You have trailing whitespace. Please run your patches through
scripts/checkpatch.pl.

> +				    "SLEEP_CFM: dev_alloc_skb failed\n");
> +			return -ENOMEM;

It's not exactly a problem with your patch, but nobody really checks the
return status of this function. I think in most (all?) cases, that's
probably OK, because we also implicitly communicate the success/failure
of this function by modifying the ->ps_state field (basically, a state
machine). So this is probably OK.

Other than the whitespace:

Reviewed-by: Brian Norris <briannorris@...omium.org>

> +		}
> +
>  		skb_put(sleep_cfm_tmp, sizeof(struct mwifiex_opt_sleep_confirm)
>  			+ MWIFIEX_TYPE_LEN);
>  		put_unaligned_le32(MWIFIEX_USB_TYPE_CMD, sleep_cfm_tmp->data);
> -- 
> 2.17.1
>