[PATCH ath-next v2] wifi: ath12k: Abort scan before removing link interface to prevent duplicate deletion

[Lorenzo Stoakes]

On Mon, Apr 14, 2025 at 11:27:47AM +0800, Lingbo Kong wrote:
>
>
> On 2025/4/11 18:05, Lorenzo Stoakes wrote:
> > +cc Oleskandr who kindly pointed me at the v1 of this patch (see [0]).
> >
> > [0]:https://lore.kernel.org/all/20250124093352.481-1-quic_lingbok@quicinc.com/
> >
> > On Wed, Feb 26, 2025 at 07:31:18PM +0800, Lingbo Kong wrote:
> > > Currently, when ath12k performs the remove link interface operation, if
> > > there is an ongoing scan operation on the arvif, ath12k may execute the
> > > remove link interface operation multiple times on the same arvif. This
> > > occurs because, during the remove link operation, if a scan operation is
> > > present on the arvif, ath12k may receive a WMI_SCAN_EVENT_COMPLETED event
> > > from the firmware. Upon receiving this event, ath12k will continue to
> > > execute the ath12k_scan_vdev_clean_work() function, performing the remove
> > > link interface operation on the same arvif again.
> > >
> > > To address this issue, before executing the remove link interface
> > > operation, ath12k needs to check if there is an ongoing scan operation on
> > > the current arvif. If such an operation exists, it should be aborted.
> > >
> > > Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
> > >
> > > Signed-off-by: Lingbo Kong <quic_lingbok at quicinc.com>
> >
> > Hey, thanks for this!
> >
> > Not sure on status of this, has the patch been taken for 6.15? As I don't
> > see it in Linus's tree (not looking _that_ hard though). I don't think it's
> > even in -next?
> >
> > I keep hitting issues with my X870E CARBON wifi onboard motherboard wifi -
> > most recently I saw a null pointer deref in ath12k_mac_remove_link_interface().
> >
> > This occurred when I tried changing the network interface, in fact I had
> > first clicked on 'available networks' in network manager so quite likely a
> > concurrent scan.
> >
> > I rather stupidly didn't copy/paste the text of it, but you can see the
> > report in screenshot form at [1]. Apologies for shade being case on ath12k
> > driver but you know, frustrations :))
> >
> > It's difficult for me to test your patch as I am having pretty awful
> > firmware issue with this motherboard - if I powercycle in any way that gets
> > interrupted, or especially if a kernel issue arises, then the ath12k module
> > will not load on next boot, or at all going forward.
> >
> > Updating the kernel to, I think, a recent 6.13 (and now 6.14-1 where I
> > observed this issue), got the wifi working again, seemingly randomly.
> >
> > Usually I have to try to reset the CMOS state, but doing so causes other
> > issues so I generally try to avoid (I have a network workaround involving
> > an ethernet wifi adapater, it's pretty... yeah).
> >
> > So I assume some non-volatile state gets corrupted somehow, I'm not sure if
> > you had any insights into how I might more sanely reset that?
> >
> > Anyway regardless thanks for your efforts, if the wifi adapter appears
> > again then I will test this and can give T-b tags if so.
> >
> > Cheers, Lorenzo
> >
> > [1]:https://fosstodon.org/@ljs/114318530969496869
> >
>
> hi, lorenzo,
> sry for delay response.😊
> as for as i know, this patch hasn't been accepted so far.
> for your description, you find the ath12k_mac_remove_link_interface() have a
> null pointer deref, i think maybe there is a concurrent scan operation.
>
> i have a suggestion, you can apply this patch and observe if there is still
> a crash.

Unfortunately as I said it's really hard for me to test this since the
motherboard wifi is permanently unavailable due to some cmos state which is
really painful/difficult for me to restore.

This is another bug/issue specific I guess to my motherboard.

I can give it a try if/when that ever comes back, but I really can't afford
unfortunately on this machine the time/risk to try to reset mobo state as things
become unstable when I try.

>
> can you offer a detailed crash dump?

Again, unfortunately, all I can offer is that screenshot I took, I stupidly
didn't copy/paste it.

And it seems kernel I was using had symbols stripped so hard to figure out
exactly where in function it occurred.

>
> /lingbo
>
>
> > > ---
> > > 1.rebase to ath-next
> > >
> > >   drivers/net/wireless/ath/ath12k/mac.c | 5 +++++
> > >   1 file changed, 5 insertions(+)
> > >
> > > diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
> > > index 3e3afdc56fc9..551133483f44 100644
> > > --- a/drivers/net/wireless/ath/ath12k/mac.c
> > > +++ b/drivers/net/wireless/ath/ath12k/mac.c
> > > @@ -9578,6 +9578,11 @@ ath12k_mac_op_unassign_vif_chanctx(struct ieee80211_hw *hw,
> > >   	if (ahvif->vdev_type != WMI_VDEV_TYPE_MONITOR &&
> > >   	    ar->num_started_vdevs == 1 && ar->monitor_vdev_created)
> > >   		ath12k_mac_monitor_stop(ar);
> > > +
> > > +	if (ar->scan.arvif == arvif && ar->scan.state == ATH12K_SCAN_RUNNING) {
> > > +		ath12k_scan_abort(ar);
> > > +		ar->scan.arvif = NULL;
> > > +	}
> > >   }
> > >
> > >   static int
> > >
> > > base-commit: e180a01bf2c4a67db13d70d2d91410a8c6f74be3
> > > --
> > > 2.34.1
> > >
> > >