kernel panic due to a missing work initialization in case of zero

[Hou Pu]

On 4/20/21 11:46, Engel, Amit wrote:
> Hello,
> 
> We hit a kernel panic as a result of the below sequence:
> In the current nvmet implementation, as part of 'nvmet_start_keep_alive_timer'
> nvmet_keep_alive_timer work will be initialized only if kato != 0
> 
> when nvme connect cmd is being executed with a zero kato value
> 'INIT_DELAYED_WORK(&ctrl->ka_work, nvmet_keep_alive_timer)' will not be called
> 
> once keep alive cmd arrives, we call 'mod_delayed_work' for a work that has not been initialized
> this will lead to kernel WARNING:
> Apr 20 10:32:59 FNM00190700796-A kernel: WARNING: CPU: 11 PID: 75133 at kernel/workqueue.c:1447 __queue_work.cold.55+0xc/0x3c
> And eventually to soft lockup

Hello Engel,

Could you verify this with latest nvme-5.13 branch? I think this
might be the same problem as commit 7b96918a173 (nvmet: avoid
queuing keep-alive timer if it is disabled) fixed.

Thanks,
Hou

> 
> A simple fix for this issue (I will post a patch soon) is to initialize the work (as part of 'nvmet_start_keep_alive_timer') even if kato == 0
> 
> Thanks
> Amit E