[PATCH v3 2/2] Bluetooth: fix inconsistent lock state in rfcomm_connect_ind

Desmond Cheong Zhi Xi desmondcheongzx at gmail.com
Fri Jul 30 09:06:09 UTC 2021

Hi Marcel,

On 30/7/21 3:53 am, Marcel Holtmann wrote:
> Hi Desmond,
>> Commit fad003b6c8e3d ("Bluetooth: Fix inconsistent lock state with
>> RFCOMM") fixed a lockdep warning due to sk->sk_lock.slock being
>> acquired without disabling softirq while the lock is also used in
>> softirq context. This was done by disabling interrupts before calling
>> bh_lock_sock in rfcomm_sk_state_change.
>> Later, this was changed in commit e6da0edc24ee ("Bluetooth: Acquire
>> sk_lock.slock without disabling interrupts") to disable softirqs
>> only.
>> However, there is another instance of sk->sk_lock.slock being acquired
>> without disabling softirq in rfcomm_connect_ind. This patch fixes this
>> by disabling local bh before the call to bh_lock_sock.
> back in the days, the packet processing was done in a tasklet, but these days it is done in a workqueue. So shouldn’t this be just converted into a lock_sock(). Am I missing something?

Thanks for the info. I think you're right, I just didn't understand very 
much when I wrote this patch.

If I'm understanding correctly, it seems that both the bh_lock_sock in 
rfcomm_connect_ind, and spin_lock_bh in rfcomm_sk_state_change need to 
be changed to lock_sock, otherwise they don't provide any 
synchronization with other functions in RFCOMM that use lock_sock.

If that sounds correct I can prepare the patch for that.

Best wishes,

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