Re: [PATCH] staging: rtl8723bs: Fix uninitialized variable

From: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Wenli Looi <wlooi@ucalgary.ca>
Cc: linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] staging: rtl8723bs: Fix uninitialized variable
Date: Sun, 06 Jun 2021 10:00:18 +0200	[thread overview]
Message-ID: <10029109.FgdUXNWx4t@linux.local> (raw)
In-Reply-To: <CAKe_nd2q8caqND=z9Pq7Me_BtyuCd2-Nb_xyepsjDkaPkC8Few@mail.gmail.com>

On Sunday, June 6, 2021 9:51:35 AM CEST Wenli Looi wrote:
> On Sun, Jun 6, 2021 at 12:13 AM Greg Kroah-Hartman
> 
> <gregkh@linuxfoundation.org> wrote:
> > On Sun, Jun 06, 2021 at 12:00:21AM -0700, Wenli Looi wrote:
> > > Uninitialized struct with invalid pointer causes BUG and prevents access
> > > point from working. Access point works once I apply this patch.
> > > 
> > > https://forum.armbian.com/topic/14727-wifi-ap-kernel-bug-in-kernel-5444/
> > > has more details.
> > > 
> > > Signed-off-by: Wenli Looi <wlooi@ucalgary.ca>
> > > ---
> > > 
> > >  drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
> > > b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c index 2fb80b6eb..
7308e1185
> > > 100644
> > > --- a/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
> > > +++ b/drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c
> > > @@ -2384,7 +2384,7 @@ void rtw_cfg80211_indicate_sta_assoc(struct 
adapter *padapter,
> > > u8 *pmgmt_frame,> > 
> > >       DBG_871X(FUNC_ADPT_FMT"\n", FUNC_ADPT_ARG(padapter));
> > >       
> > >       {
> > > 
> > > -             struct station_info sinfo;
> > > +             struct station_info sinfo = {};
> > 
> > What caused this bug to show up?  Did it happen from some other commit?
> > 
> > Are you sure that all of the fields are being cleared properly here,
> > what about any "holes" in the structure?
> > 
> > thanks,
> > greg k-h
> 
> I believe this bug has been present since the driver was added to
> staging:
> https://github.com/torvalds/linux/commit/
554c0a3abf216c991c5ebddcdb2c08689ecd290b
> 
> It's probably not necessary to zero the entire struct, only
> sinfo->pertid, which causes problems with the code here:
> https://github.com/torvalds/linux/blob/
f5b6eb1e018203913dfefcf6fa988649ad11ad6e/net/wire
> less/nl80211.c#L5919
> 
> You can see the following proposed OpenWrt patch
> (700-wifi-8723bs-ap-bugfix.patch in
> https://github.com/openwrt/openwrt/pull/4053/files) which sets
> sinfo.pertid = 0; instead of zeroing the struct.
> 
> Looking at similar code in a non-staging driver, we can see that the
> code there zeros the struct using kzalloc():
> https://github.com/torvalds/linux/blob/
f5b6eb1e018203913dfefcf6fa988649ad11ad6e/drivers/
> net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c#L6064
> 
> Do you think kzalloc() would be preferable?
>
You cannot use kzalloc there: 'sinfo' is instantiated automatically on the 
stack. The example you took had a pointer to the struct. 

Fabio
> 
> Sorry, I'm not familiar with "holes" in the struct.