linux-kernel - Re: [PATCH v2] ath9k_htc: Add a missing spin_lock

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Date:   Mon, 20 Dec 2021 15:50:16 +0000 (UTC)
From:   Kalle Valo <kvalo@...nel.org>
To:     Rajat Asthana <rajatasthana4@...il.com>
Cc:     ath9k-devel@....qualcomm.com, kvalo@...eaurora.org,
        davem@...emloft.net, kuba@...nel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Rajat Asthana <rajatasthana4@...il.com>
Subject: Re: [PATCH v2] ath9k_htc: Add a missing spin_lock_init()

Rajat Asthana <rajatasthana4@...il.com> wrote:

> Syzkaller reported a lockdep warning on non-initialized spinlock:
> 
> INFO: trying to register non-static key.
> The code is fine but needs lockdep annotation, or maybe
> you didn't initialize this object before use?
> turning off the locking correctness validator.
> CPU: 0 PID: 10 Comm: ksoftirqd/0 Not tainted 5.13.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x143/0x1db lib/dump_stack.c:120
>  assign_lock_key kernel/locking/lockdep.c:937 [inline]
>  register_lock_class+0x1077/0x1180 kernel/locking/lockdep.c:1249
>  __lock_acquire+0x102/0x5230 kernel/locking/lockdep.c:4781
>  lock_acquire kernel/locking/lockdep.c:5512 [inline]
>  lock_acquire+0x19d/0x700 kernel/locking/lockdep.c:5477
>  __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
>  _raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:175
>  spin_lock_bh include/linux/spinlock.h:359 [inline]
>  ath9k_wmi_event_tasklet+0x231/0x3f0 drivers/net/wireless/ath/ath9k/wmi.c:172
>  tasklet_action_common.constprop.0+0x201/0x2e0 kernel/softirq.c:784
>  __do_softirq+0x1b0/0x944 kernel/softirq.c:559
>  run_ksoftirqd kernel/softirq.c:921 [inline]
>  run_ksoftirqd+0x21/0x50 kernel/softirq.c:913
>  smpboot_thread_fn+0x3ec/0x870 kernel/smpboot.c:165
>  kthread+0x38c/0x460 kernel/kthread.c:313
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
> 
> We missed a spin_lock_init() in ath9k_wmi_event_tasklet() when the wmi
> event is WMI_TXSTATUS_EVENTID. So, add a spin_lock_init() in
> ath9k_init_wmi().
> 
> Signed-off-by: Rajat Asthana <rajatasthana4@...il.com>
> Signed-off-by: Kalle Valo <quic_kvalo@...cinc.com>

The lock is already initialised in ath9k_init_priv(), so now the same lock is
initialised twice. ath9k_init_wmi() is called before ath9k_init_priv(), so it
looks like we have a race somewhere.

Patch set to Changes Requested.

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20210728192533.18727-1-rajatasthana4@gmail.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches