Re: [regression] mt76x2u: NULL pointer dereference since recent change to fix chanctx emulation for monitor mode

[Johannes Berg <johannes@sipsolutions.net>]

On Wed, 2024-07-24 at 09:58 +0200, Linux regression tracking (Thorsten
Leemhuis) wrote:
> Hi, Thorsten here, the Linux kernel's regression tracker.
> 
> Johannes, Felix, Lorenzo, Ryder, I noticed a report about a regression
> in bugzilla.kernel.org that (for my untrained eyes) appears to be a bug
> in some code paths of mt76x2u that was exposed by 0d9c2beed116e6 ("wifi:
> mac80211: fix monitor channel with chanctx emulation") [v6.10-rc5,
> v6.9.7] from Johannes.
> 
> As many (most?) kernel developers don't keep an eye on the bug tracker,
> I decided to write this mail. To quote from
> https://bugzilla.kernel.org/show_bug.cgi?id=219086 :
> 
> >  Michael 2024-07-23 15:38:43 UTC
> > 
> > After a user opened this discussion:
> > https://github.com/ZerBea/hcxdumptool/discussions/465
> > 
> > Jul 21 05:40:39 rpi4b-aarch kernel: mt76x2u 2-2:1.0 wlan1: entered promiscuous mode
> > Jul 21 05:40:45 rpi4b-aarch kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> > Jul 21 05:40:45 rpi4b-aarch kernel: Mem abort info:
> > Jul 21 05:40:45 rpi4b-aarch kernel:   ESR = 0x0000000096000044
> > Jul 21 05:40:45 rpi4b-aarch kernel:   EC = 0x25: DABT (current EL), IL = 32 bits
> > Jul 21 05:40:45 rpi4b-aarch kernel:   SET = 0, FnV = 0
> > Jul 21 05:40:45 rpi4b-aarch kernel:   EA = 0, S1PTW = 0
> > Jul 21 05:40:45 rpi4b-aarch kernel:   FSC = 0x04: level 0 translation fault
> > Jul 21 05:40:45 rpi4b-aarch kernel: Data abort info:
> > Jul 21 05:40:45 rpi4b-aarch kernel:   ISV = 0, ISS = 0x00000044, ISS2 = 0x00000000
> > Jul 21 05:40:45 rpi4b-aarch kernel:   CM = 0, WnR = 1, TnD = 0, TagAccess = 0
> > Jul 21 05:40:45 rpi4b-aarch kernel:   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> > Jul 21 05:40:45 rpi4b-aarch kernel: user pgtable: 4k pages, 48-bit VAs, pgdp=0000000041300000
> > 

Not too well-versed with ARM, does that tel me anything about where in
the code the crash was? Without any further information I don't think I
can see anything here, and I don't have an affected device.

johannes