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

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Message-ID: <20220726134309.qiloewsgtkojf6yq@skbuf>
Date:   Tue, 26 Jul 2022 16:43:09 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com, edumazet@...gle.com, andrew@...n.ch,
        vivien.didelot@...il.com, f.fainelli@...il.com
Subject: Re: [patch net-next RFC] net: dsa: move port_setup/teardown to be
 called outside devlink port registered area

Hi Jiri,

On Tue, Jul 26, 2022 at 02:41:05PM +0200, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@...dia.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@...dia.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