Re: [PATCH] rtw88: fix use after free in rtw_hw_scan_update_probe_req()

[Dan Carpenter <dan.carpenter@oracle.com>]

On Thu, Feb 03, 2022 at 07:59:47AM +0000, Pkshih wrote:
> On Wed, 2022-02-02 at 16:05 +0300, Dan Carpenter wrote:
> > This code needs to use skb_queue_walk_safe() instead of skb_queue_walk()
> > because it frees the list iterator.
> > 
> > Fixes: d95984b5580d ("rtw88: fix memory overrun and memory leak during hw_scan")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> >  drivers/net/wireless/realtek/rtw88/fw.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/realtek/rtw88/fw.c b/drivers/net/wireless/realtek/rtw88/fw.c
> > index ce9535cce723..2de0bb67bac6 100644
> > --- a/drivers/net/wireless/realtek/rtw88/fw.c
> > +++ b/drivers/net/wireless/realtek/rtw88/fw.c
> > @@ -1864,7 +1864,7 @@ static int rtw_hw_scan_update_probe_req(struct rtw_dev *rtwdev,
> >  {
> >  	struct cfg80211_scan_request *req = rtwvif->scan_req;
> >  	struct sk_buff_head list;
> > -	struct sk_buff *skb;
> > +	struct sk_buff *skb, *tmp;
> >  	u8 num = req->n_ssids, i, bands = 0;
> >  	int ret;
> >  
> > @@ -1889,7 +1889,7 @@ static int rtw_hw_scan_update_probe_req(struct rtw_dev *rtwdev,
> >  	return _rtw_hw_scan_update_probe_req(rtwdev, num * bands, &list);
> >  
> >  out:
> > -	skb_queue_walk(&list, skb)
> > +	skb_queue_walk_safe(&list, skb, tmp)
> >  		kfree_skb(skb);
> >  
> >  	return ret;
> 
> 
> Oops, when I reivewed the patch "rtw88: fix memory overrun and memory leak during hw_scan", 
> I did only focus on pointers of list head, but forget skb is freed that leads use after free.
> 
> Could I have related fix with this patch?
> 

Yes, thank you for noticing that.  For some reason, on my system, Smatch
thinks that probe_req_list is always empty and doesn't warn about that
one because "it's impossible".

I will send a v2 patch.

regards,
dan carpenter