Re: [PATCH] wireless/marvell/mwifiex: Fix a double free in mwifiex_send_tdls_action_frame

[Brian Norris <briannorris@chromium.org>]

Hi,

On Wed, Apr 14, 2021 at 12:08:32AM +0800, lyl2019@mail.ustc.edu.cn wrote:
> 
> Hi,
>   maintianers.
> 
>   Sorry to disturb you, but this patch seems to be missed more than two weeks.
>   Could you help to review this patch? I am sure it won't take you much time.

You might take a look here:
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches#checking_state_of_patches_from_patchwork
https://patchwork.kernel.org/project/linux-wireless/list/

Two weeks is not unheard of for waiting.

Anyway, you *did* succeed in catching my attention today, so I'll give
you a review, below:

> > -----原始邮件-----
> > 发件人: "Lv Yunlong" <lyl2019@mail.ustc.edu.cn>
> > 发送时间: 2021-03-29 19:24:35 (星期一)
> > 收件人: amitkarwar@gmail.com, ganapathi.bhat@nxp.com, huxinming820@gmail.com, kvalo@codeaurora.org, davem@davemloft.net, kuba@kernel.org
> > 抄送: linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Lv Yunlong" <lyl2019@mail.ustc.edu.cn>
> > 主题: [PATCH] wireless/marvell/mwifiex: Fix a double free in mwifiex_send_tdls_action_frame
> > 
> > In mwifiex_send_tdls_action_frame, it calls mwifiex_construct_tdls_action_frame
> > (..,skb). The skb will be freed in mwifiex_construct_tdls_action_frame() when
> > it is failed. But when mwifiex_construct_tdls_action_frame() returns error,
> > the skb will be freed in the second time by dev_kfree_skb_any(skb).
> > 
> > My patch removes the redundant dev_kfree_skb_any(skb) when
> > mwifiex_construct_tdls_action_frame() failed.
> > 
> > Fixes: b23bce2965680 ("mwifiex: add tdls_mgmt handler support")
> > Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
> > ---
> >  drivers/net/wireless/marvell/mwifiex/tdls.c | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/drivers/net/wireless/marvell/mwifiex/tdls.c b/drivers/net/wireless/marvell/mwifiex/tdls.c
> > index 97bb87c3676b..8d4d0a9cf6ac 100644
> > --- a/drivers/net/wireless/marvell/mwifiex/tdls.c
> > +++ b/drivers/net/wireless/marvell/mwifiex/tdls.c
> > @@ -856,7 +856,6 @@ int mwifiex_send_tdls_action_frame(struct mwifiex_private *priv, const u8 *peer,
> >  	if (mwifiex_construct_tdls_action_frame(priv, peer, action_code,
> >  						dialog_token, status_code,
> >  						skb)) {
> > -		dev_kfree_skb_any(skb);

Good catch, and this looks correct for most cases, but I'll note that
you missed one issue: mwifiex_construct_tdls_action_frame() has a
default/error case ("Unknown TDLS action frame type") which does *not*
free this SKB, so you should patch that up at the same time. Otherwise,
you're trading a double-free for a potential memory leak.

With that fixed:

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

Thanks.

> >  		return -EINVAL;
> >  	}
> >  
> > -- 
> > 2.25.1
> >