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

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Message-ID: <231c6ea5-b8a3-4500-b994-46a45b6ab515@gmx.de>
Date: Thu, 25 Jul 2024 17:54:05 +0200
From: ZeroBeat <ZeroBeat@....de>
To: Johannes Berg <johannes@...solutions.net>,
 Linux regressions mailing list <regressions@...ts.linux.dev>,
 Felix Fietkau <nbd@....name>, Lorenzo Bianconi <lorenzo@...nel.org>,
 Ryder Lee <ryder.lee@...iatek.com>
Cc: "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>, Kalle Valo <kvalo@...nel.org>
Subject: Re: [regression] mt76x2u: NULL pointer dereference since recent
 change to fix chanctx emulation for monitor mode

Just to mention it here. The regression has now reached the longterm kernel:
affected devices: mt76 series (not affected mt7601u)


before update:
$ uname -r
6.6.40-2-lts

$ sudo hcxdumptool -i wlp5s0f4u2 --rcascan=active
^C
38 Packet(s) captured by kernel
0 Packet(s) dropped by kernel
14 PROBERESPONSE(s) captured

exit on sigterm



after update:
$ uname -r
6.6.41-1-lts

$ sudo hcxdumptool -i wlp48s0f4u2u1 --rcascan=active
^C
0 Packet(s) captured by kernel
0 Packet(s) dropped by kernel
Warning: too less packets received (monitor mode may not work as expected)
Possible reasons:
  no transmitter in range
  frames are filtered out by BPF
  driver is broken
Warning: no PROBERESPONSES received (frame injection may not work as expected)
Possible reasons:
  no AP in range
  frames are filtered out by BPF
  driver is broken
  driver does not support frame injection

exit on sigterm


Best regards
Mike






Am 24.07.24 um 10:47 schrieb Johannes Berg:
> 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

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