On Thu, Aug 22, 2024 at 01:34:33PM +0200, Maciej Fijalkowski wrote:
> On Mon, Aug 19, 2024 at 12:05:41PM +0200, Larysa Zaremba wrote:
> > Consider the following scenario:
> >
> > .ndo_bpf() | ice_prepare_for_reset() |
> > ________________________|_______________________________________|
> > rtnl_lock() | |
> > ice_down() | |
> > | test_bit(ICE_VSI_DOWN) - true |
> > | ice_dis_vsi() returns |
> > ice_up() | |
> > | proceeds to rebuild a running VSI |
> >
> > .ndo_bpf() is not the only rtnl-locked callback that toggles the interface
> > to apply new configuration. Another example is .set_channels().
> >
> > To avoid the race condition above, act only after reading ICE_VSI_DOWN
> > under rtnl_lock.
> >
> > Fixes: 0f9d5027a749 ("ice: Refactor VSI allocation, deletion and rebuild flow")
> > Reviewed-by: Wojciech Drewek <wojciech.drewek@xxxxxxxxx>
> > Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
> > Tested-by: Chandan Kumar Rout <chandanx.rout@xxxxxxxxx>
> > Signed-off-by: Larysa Zaremba <larysa.zaremba@xxxxxxxxx>
> > ---
> > drivers/net/ethernet/intel/ice/ice_lib.c | 12 ++++++------
> > 1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
> > index b72338974a60..94029e446b99 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_lib.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_lib.c
> > @@ -2665,8 +2665,7 @@ int ice_ena_vsi(struct ice_vsi *vsi, bool locked)
> > */
> > void ice_dis_vsi(struct ice_vsi *vsi, bool locked)
> > {
> > - if (test_bit(ICE_VSI_DOWN, vsi->state))
> > - return;
> > + bool already_down = test_bit(ICE_VSI_DOWN, vsi->state);
> >
> > set_bit(ICE_VSI_NEEDS_RESTART, vsi->state);
> >
> > @@ -2674,15 +2673,16 @@ void ice_dis_vsi(struct ice_vsi *vsi, bool locked)
> > if (netif_running(vsi->netdev)) {
> > if (!locked)
> > rtnl_lock();
> > -
> > - ice_vsi_close(vsi);
> > + already_down = test_bit(ICE_VSI_DOWN, vsi->state);
> > + if (!already_down)
> > + ice_vsi_close(vsi);
>
> ehh sorry for being sloppy reviewer. we still are testing ICE_VSI_DOWN in
> ice_vsi_close(). wouldn't all of this be cleaner if we would bail out of
> the called function when bit was already set?
>
I am not sure I see the possibility to rewrite this as you suggest, we cannot
bail out for the netif_running() case due to needing to unlock after
ice_vsi_close() finishes. This leaves bailing out in case of CTRL VSI and
non-running PF, which we could do, but it would require a lengthy if condition,
which is not that much better than nested code, IMO.
> >
> > if (!locked)
> > rtnl_unlock();
> > - } else {
> > + } else if (!already_down) {
> > ice_vsi_close(vsi);
> > }
> > - } else if (vsi->type == ICE_VSI_CTRL) {
> > + } else if (vsi->type == ICE_VSI_CTRL && !already_down) {
> > ice_vsi_close(vsi);
> > }
> > }
> > --
> > 2.43.0
> >
