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

Marcel Holtmann marcel at holtmann.org
Fri Jul 30 13:40:19 UTC 2021


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.

please do so and re-run the tests. Thanks.

Regards

Marcel



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