linux-kernel - Re: [PATCH] staging: rtl8192e: Fix possible buffer overflow in _rtl92e_wx_set

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Date:   Fri, 26 Feb 2021 15:30:22 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Lee Gibson <leegib@...il.com>, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8192e: Fix possible buffer overflow in
 _rtl92e_wx_set_scan

On Fri, Feb 26, 2021 at 01:06:46PM +0100, Greg KH wrote:
> On Fri, Feb 26, 2021 at 11:48:29AM +0000, Lee Gibson wrote:
> > Function _rtl92e_wx_set_scan calls memcpy without checking the length.
> > A user could control that length and trigger a buffer overflow.
> > Fix by checking the length is within the maximum allowed size.
> > 
> > Signed-off-by: Lee Gibson <leegib@...il.com>
> > ---
> >  drivers/staging/rtl8192e/rtl8192e/rtl_wx.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/staging/rtl8192e/rtl8192e/rtl_wx.c b/drivers/staging/rtl8192e/rtl8192e/rtl_wx.c
> > index 16bcee13f64b..2acc4f314732 100644
> > --- a/drivers/staging/rtl8192e/rtl8192e/rtl_wx.c
> > +++ b/drivers/staging/rtl8192e/rtl8192e/rtl_wx.c
> > @@ -406,6 +406,9 @@ static int _rtl92e_wx_set_scan(struct net_device *dev,
> >  		struct iw_scan_req *req = (struct iw_scan_req *)b;
> >  
> >  		if (req->essid_len) {
> > +			if (req->essid_len > IW_ESSID_MAX_SIZE)
> > +				req->essid_len = IW_ESSID_MAX_SIZE;
> > +
> 
> How about using the "pattern" the other wireless drivers use of:
> 
> 		int len = min((int)req->essid_len, IW_ESSID_MAX_SIZE);


I bet checkpatch complains that we should use min_t() instead (but I'm
too lazy to verify).

	int len = min_t(int, req->essid_len, IW_ESSID_MAX_SIZE);

regards,
dan carpenter