Messages in this thread | | | Date | Wed, 20 Apr 2022 09:36:43 +0300 | From | Leon Romanovsky <> | Subject | Re: [PATCH net] ice: Fix race during aux device (un)plugging |
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On Fri, Apr 15, 2022 at 05:49:32PM +0200, Ivan Vecera wrote: > On Fri, 15 Apr 2022 13:12:03 +0200 > Michal Schmidt <mschmidt@redhat.com> wrote: > > > On Thu, Apr 14, 2022 at 6:39 PM Ivan Vecera <ivecera@redhat.com> wrote: > > > > > Function ice_plug_aux_dev() assigns pf->adev field too early prior > > > aux device initialization and on other side ice_unplug_aux_dev() > > > starts aux device deinit and at the end assigns NULL to pf->adev. > > > This is wrong and can causes a crash when ice_send_event_to_aux() > > > call occurs during these operations because that function depends > > > on non-NULL value of pf->adev and does not assume that aux device > > > is half-initialized or half-destroyed. > > > > > > Modify affected functions so pf->adev field is set after aux device > > > init and prior aux device destroy. > > > > > [...] > > > > > @@ -320,12 +319,14 @@ int ice_plug_aux_dev(struct ice_pf *pf) > > > */ > > > void ice_unplug_aux_dev(struct ice_pf *pf) > > > { > > > - if (!pf->adev) > > > + struct auxiliary_device *adev = pf->adev; > > > + > > > + if (!adev) > > > return; > > > > > > - auxiliary_device_delete(pf->adev); > > > - auxiliary_device_uninit(pf->adev); > > > pf->adev = NULL; > > > + auxiliary_device_delete(adev); > > > + auxiliary_device_uninit(adev); > > > } > > > > > > > Hi Ivan, > > What prevents ice_unplug_aux_dev() from running immediately after > > ice_send_event_to_aux() gets past its "if (!pf->adev)" test ? > > Michal > > ice_send_event_to_aux() takes aux device lock. ice_unplug_aux_dev() > calls auxiliary_device_delete() that calls device_del(). device_del() > takes device_lock() prior kill_device(). So if ice_send_event_to_aux() > is in progress then device_del() waits for its completion.
Not really, you nullify pf->adev without any lock protection and ice_send_event_to_aux() will simply crash.
CPU#1 | CPU#2 | ice_send_event_to_aux ice_unplug_aux_dev() | ... ... | pf->adev = NULL; | | device_lock(&pf->adev->dev); <--- crash here.
Thanks
> > Thanks, > Ivan >
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