Re: [patch net-next RFC] net: dsa: move port_setup/teardown to be called outside devlink port registered area

Vladimir Oltean
2022-07-26T13:45:13Z

Hi Jiri,

On Tue, Jul 26, 2022 at 02:41:05PM +0200, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@nvidia.com>
>
> Move port_setup() op to be called before devlink_port_register() and
> port_teardown() after devlink_port_unregister().
>
> RFC note: I don't see why this would not work, but I have no way to
> test this does not break things. But I think it makes sense to move this
> alongside the rest of the devlink port code, the reinit() function
> also gets much nicer, as clearly the fact that
> port_setup()->devlink_port_region_create() was called in dsa_port_setup
> did not fit the flow.
>
> Signed-off-by: Jiri Pirko <jiri@nvidia.com>
> ---

devlink_port->devlink isn't set (it's set in devl_port_register), so
when devlink_port_region_create() calls devl_lock(devlink), it blasts
right through that NULL pointer:

[ 4.966960] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000320
[ 5.009201] [0000000000000320] user address but active_mm is swapper
[ 5.015616] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[ 5.024244] CPU: 1 PID: 8 Comm: kworker/u4:0 Not tainted 5.19.0-rc7-07010-ga9b9500ffaac-dirty #3395
[ 5.033281] Hardware name: CZ.NIC Turris Mox Board (DT)
[ 5.038499] Workqueue: events_unbound deferred_probe_work_func
[ 5.044342] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 5.051297] pc : __mutex_lock+0x5c/0x460
[ 5.055220] lr : __mutex_lock+0x50/0x460
[ 5.133818] Call trace:
[ 5.136258] __mutex_lock+0x5c/0x460
[ 5.139831] mutex_lock_nested+0x40/0x50
[ 5.143750] devlink_port_region_create+0x54/0x15c
[ 5.148542] dsa_devlink_port_region_create+0x64/0x90
[ 5.153592] mv88e6xxx_setup_devlink_regions_port+0x30/0x60
[ 5.159165] mv88e6xxx_port_setup+0x10/0x20
[ 5.163345] dsa_port_devlink_setup+0x60/0x150
[ 5.167786] dsa_register_switch+0x938/0x119c
[ 5.172138] mv88e6xxx_probe+0x714/0x770
[ 5.176058] mdio_probe+0x34/0x70
[ 5.179370] really_probe.part.0+0x9c/0x2ac
[ 5.183550] __driver_probe_device+0x98/0x144
[ 5.187902] driver_probe_device+0xac/0x14c