[lkml]   [2019]   [Jul]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 0/2] Fix use-after-free bug when ports are removed

On 2019-07-03 1:20 p.m., Sagi Grimberg wrote:
>>> Can we handle this in the core instead (also so we'd be consistent
>>> across transports)?
>> Yes, that would be much better if we can sort out some other issues
>> below...
>>> How about this untested patch instead?
>> I've found a couple of problems with the patch:
>> 1) port->subsystems will always be empty before nvmet_disable_port() is
>> called. We'd have to restructure things a little perhaps so that when a
>> subsystem is removed from a port, all the active controllers for that
>> subsys/port combo would be removed.
> Yes, that is better.

Ok, if you like this solution I'll try and come up with a patch like
that. It *may* not be too intrusive compared to the cleanup I suggested

>> 2) loop needs to call flush_workqueue(nvme_delete_wq) somewhere,
>> otherwise there's a small window after the port disappears while
>> commands can still be submitted. We can actually still hit the bug with
>> a tight loop.
> We could simply flush the workqueue in nvme_loop_delete_ctrl for
> each controller?
> Might be an overkill though, and its risking circular locking in case
> we are going via the fatal error path (work context flushing a different
> workqueue always annoys lockdep even when its perfectly safe)
>> Maybe there's other cleanup that could be done to solve this: it does
>> seem like all three transports need to keep their own lists of open
>> controllers and loops through them to delete them. In theory, that could
>> be made common so there's common code to manage the list per transport
>> which would remove some boiler plate code. If we want to go this route
>> though, I'd suggest using my patches as is for now and doing the cleanup
>> in the next cycle.
> Then please fix tcp as well.

Ok, I'll try to send either a destroy controller on subsystem-removal
patch or I'll resend these with TCP included sometime today or tomorrow.



 \ /
  Last update: 2019-07-03 21:25    [W:0.157 / U:0.968 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site