RE: [PATCH v2] ath10k: Fix the parsing error in service available event

["Rakesh Pillai" <pillair@codeaurora.org>]

> -----Original Message-----
> From: Doug Anderson <dianders@chromium.org>
> Sent: Thursday, October 29, 2020 12:15 AM
> To: Rakesh Pillai <pillair@codeaurora.org>
> Cc: ath10k <ath10k@lists.infradead.org>; linux-wireless <linux-
> wireless@vger.kernel.org>; LKML <linux-kernel@vger.kernel.org>; Abhishek
> Kumar <kuabhs@chromium.org>; Brian Norris <briannorris@chromium.org>
> Subject: Re: [PATCH v2] ath10k: Fix the parsing error in service available
> event
> 
> Hi,
> 
> On Wed, Oct 28, 2020 at 10:01 AM Rakesh Pillai <pillair@codeaurora.org>
> wrote:
> >
> > The wmi service available event has been
> > extended to contain extra 128 bit for new services
> > to be indicated by firmware.
> >
> > Currently the presence of any optional TLVs in
> > the wmi service available event leads to a parsing
> > error with the below error message:
> > ath10k_snoc 18800000.wifi: failed to parse svc_avail tlv: -71
> >
> > The wmi service available event parsing should
> > not return error for the newly added optional TLV.
> > Fix this parsing for service available event message.
> >
> > Tested-on: WCN3990 hw1.0 SNOC
> >
> > Fixes: cea19a6ce8bf ("ath10k: add WMI_SERVICE_AVAILABLE_EVENT
> support")
> > Signed-off-by: Rakesh Pillai <pillair@codeaurora.org>
> > ---
> > Changes from v1:
> > - Access service_map_ext only if this TLV was sent in service
> >   available event.
> > ---
> >  drivers/net/wireless/ath/ath10k/wmi-tlv.c | 4 +++-
> >  drivers/net/wireless/ath/ath10k/wmi.c     | 5 +++--
> >  drivers/net/wireless/ath/ath10k/wmi.h     | 1 +
> >  3 files changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/wireless/ath/ath10k/wmi-tlv.c
> b/drivers/net/wireless/ath/ath10k/wmi-tlv.c
> > index 932266d..7b58341 100644
> > --- a/drivers/net/wireless/ath/ath10k/wmi-tlv.c
> > +++ b/drivers/net/wireless/ath/ath10k/wmi-tlv.c
> > @@ -1401,13 +1401,15 @@ static int
> ath10k_wmi_tlv_svc_avail_parse(struct ath10k *ar, u16 tag, u16 len,
> >
> >         switch (tag) {
> >         case WMI_TLV_TAG_STRUCT_SERVICE_AVAILABLE_EVENT:
> > +               arg->service_map_ext_valid = true;
> >                 arg->service_map_ext_len = *(__le32 *)ptr;
> >                 arg->service_map_ext = ptr + sizeof(__le32);
> >                 return 0;
> >         default:
> >                 break;
> >         }
> > -       return -EPROTO;
> > +
> > +       return 0;
> 
> I notice your v2 now returns 0 for _all_ unknown tags.  v1 just had a
> special case for "WMI_TLV_TAG_FIRST_ARRAY_ENUM".  I don't have
> enough
> experience with this driver to know which is better, but this change
> wasn't mentioned in the changes from v1.  I guess you had a change of
> heart and decided this way was better?

Earlier patchset which added a case for " WMI_TLV_TAG_FIRST_ARRAY_ENUM", still returned error if there is any other TLV except for the two cases handled.
This leaves the possibility of an error when a new TLV gets added to this service_available message.

Since we are using the "valid" flag to indicate the validity of a particular tag, we need not return failure in any case. This makes it scalable (and maintains backward compatibility), in case extra TLVs are added to this message in future.

> 
> 
> >  }
> >
> >  static int ath10k_wmi_tlv_op_pull_svc_avail(struct ath10k *ar,
> > diff --git a/drivers/net/wireless/ath/ath10k/wmi.c
> b/drivers/net/wireless/ath/ath10k/wmi.c
> > index 1fa7107..2e4b561 100644
> > --- a/drivers/net/wireless/ath/ath10k/wmi.c
> > +++ b/drivers/net/wireless/ath/ath10k/wmi.c
> > @@ -5751,8 +5751,9 @@ void ath10k_wmi_event_service_available(struct
> ath10k *ar, struct sk_buff *skb)
> >                             ret);
> >         }
> >
> > -       ath10k_wmi_map_svc_ext(ar, arg.service_map_ext, ar-
> >wmi.svc_map,
> > -                              __le32_to_cpu(arg.service_map_ext_len));
> > +       if (arg.service_map_ext_valid)
> > +               ath10k_wmi_map_svc_ext(ar, arg.service_map_ext, ar-
> >wmi.svc_map,
> > +                                      __le32_to_cpu(arg.service_map_ext_len));
> 
> Your new patch still requires the caller to init the
> "service_map_ext_valid" to false before calling, but I guess there's
> not a whole lot more we can do because we might be parsing more than
> one tag.  It does seem nice that at least we now have a validity bit
> instead of just relying on a non-zero length to be valid.
> 
> It might be nice to have a comment saying that it's up to us to init
> "arg.service_map_ext_valid" to false before calling
> ath10k_wmi_pull_svc_avail(), but I won't insist.  Maybe that's obvious
> to everyone but me...

I will wait for a couple of days, if there are any other comments, to post a v3 addressing all of them together.
This approach of having a argument initialized to parse TLVs is used for many other wmi events as well.

> 
> 
> -Doug