Message-ID: <20190807003339.GC1368@t480s.localdomain>
Date:   Wed, 7 Aug 2019 00:33:39 -0400
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     Chen-Yu Tsai <wens@...nel.org>
Cc:     Chen-Yu Tsai <wens@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v2] net: dsa: Check existence of .port_mdb_add
 callback before calling it

Hi Chen-Yu,

On Wed, 7 Aug 2019 11:18:28 +0800, Chen-Yu Tsai <wens@...nel.org> wrote:
> On Wed, Aug 7, 2019 at 4:34 AM Vivien Didelot <vivien.didelot@...il.com> wrote:
> >
> > Hi Chen-Yu,
> >
> > On Wed, 7 Aug 2019 01:49:37 +0800, Chen-Yu Tsai <wens@...nel.org> wrote:
> > > On Wed, Aug 7, 2019 at 1:15 AM Vivien Didelot <vivien.didelot@...il.com> wrote:
> > > >
> > > > Hi Chen-Yu,
> > > >
> > > > On Tue,  6 Aug 2019 15:53:25 +0800, Chen-Yu Tsai <wens@...nel.org> wrote:
> > > > > From: Chen-Yu Tsai <wens@...e.org>
> > > > >
> > > > > With the recent addition of commit 75dad2520fc3 ("net: dsa: b53: Disable
> > > > > all ports on setup"), users of b53 (BCM53125 on Lamobo R1 in my case)
> > > > > are forced to use the dsa subsystem to enable the switch, instead of
> > > > > having it in the default transparent "forward-to-all" mode.
> > > > >
> > > > > The b53 driver does not support mdb bitmap functions. However the dsa
> > > > > layer does not check for the existence of the .port_mdb_add callback
> > > > > before actually using it. This results in a NULL pointer dereference,
> > > > > as shown in the kernel oops below.
> > > > >
> > > > > The other functions seem to be properly guarded. Do the same for
> > > > > .port_mdb_add in dsa_switch_mdb_add_bitmap() as well.
> > > > >
> > > > > b53 is not the only driver that doesn't support mdb bitmap functions.
> > > > > Others include bcm_sf2, dsa_loop, lantiq_gswip, mt7530, mv88e6060,
> > > > > qca8k, realtek-smi, and vitesse-vsc73xx.
> > > >
> > > > I don't know what you mean by that, there's no "mdb bitmap function"
> > > > support for drivers, only the port_mdb_{prepare,add,del} callbacks...
> > >
> > > The term was coined from commit e6db98db8a95 ("net: dsa: add switch mdb
> > > bitmap functions"). But yeah, .port_mdb_* ops/callbacks would be more
> > > appropriate.
> > >
> > > > >     8<--- cut here ---
> > > > >     Unable to handle kernel NULL pointer dereference at virtual address 00000000
> > > > >     pgd = (ptrval)
> > > > >     [00000000] *pgd=00000000
> > > > >     Internal error: Oops: 80000005 [#1] SMP ARM
> > > > >     Modules linked in: rtl8xxxu rtl8192cu rtl_usb rtl8192c_common rtlwifi mac80211 cfg80211
> > > > >     CPU: 1 PID: 134 Comm: kworker/1:2 Not tainted 5.3.0-rc1-00247-gd3519030752a #1
> > > > >     Hardware name: Allwinner sun7i (A20) Family
> > > > >     Workqueue: events switchdev_deferred_process_work
> > > > >     PC is at 0x0
> > > > >     LR is at dsa_switch_event+0x570/0x620
> > > > >     pc : [<00000000>]    lr : [<c08533ec>]    psr: 80070013
> > > > >     sp : ee871db8  ip : 00000000  fp : ee98d0a4
> > > > >     r10: 0000000c  r9 : 00000008  r8 : ee89f710
> > > > >     r7 : ee98d040  r6 : ee98d088  r5 : c0f04c48  r4 : ee98d04c
> > > > >     r3 : 00000000  r2 : ee89f710  r1 : 00000008  r0 : ee98d040
> > > > >     Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> > > > >     Control: 10c5387d  Table: 6deb406a  DAC: 00000051
> > > > >     Process kworker/1:2 (pid: 134, stack limit = 0x(ptrval))
> > > > >     Stack: (0xee871db8 to 0xee872000)
> > > > >     1da0:                                                       ee871e14 103ace2d
> > > > >     1dc0: 00000000 ffffffff 00000000 ee871e14 00000005 00000000 c08524a0 00000000
> > > > >     1de0: ffffe000 c014bdfc c0f04c48 ee871e98 c0f04c48 ee9e5000 c0851120 c014bef0
> > > > >     1e00: 00000000 b643aea2 ee9b4068 c08509a8 ee2bf940 ee89f710 ee871ecb 00000000
> > > > >     1e20: 00000008 103ace2d 00000000 c087e248 ee29c868 103ace2d 00000001 ffffffff
> > > > >     1e40: 00000000 ee871e98 00000006 00000000 c0fb2a50 c087e2d0 ffffffff c08523c4
> > > > >     1e60: ffffffff c014bdfc 00000006 c0fad2d0 ee871e98 ee89f710 00000000 c014c500
> > > > >     1e80: 00000000 ee89f3c0 c0f04c48 00000000 ee9e5000 c087dfb4 ee9e5000 00000000
> > > > >     1ea0: ee89f710 ee871ecb 00000001 103ace2d 00000000 c0f04c48 00000000 c087e0a8
> > > > >     1ec0: 00000000 efd9a3e0 0089f3c0 103ace2d ee89f700 ee89f710 ee9e5000 00000122
> > > > >     1ee0: 00000100 c087e130 ee89f700 c0fad2c8 c1003ef0 c087de4c 2e928000 c0fad2ec
> > > > >     1f00: c0fad2ec ee839580 ef7a62c0 ef7a9400 00000000 c087def8 c0fad2ec c01447dc
> > > > >     1f20: ef315640 ef7a62c0 00000008 ee839580 ee839594 ef7a62c0 00000008 c0f03d00
> > > > >     1f40: ef7a62d8 ef7a62c0 ffffe000 c0145b84 ffffe000 c0fb2420 c0bfaa8c 00000000
> > > > >     1f60: ffffe000 ee84b600 ee84b5c0 00000000 ee870000 ee839580 c0145b40 ef0e5ea4
> > > > >     1f80: ee84b61c c014a6f8 00000001 ee84b5c0 c014a5b0 00000000 00000000 00000000
> > > > >     1fa0: 00000000 00000000 00000000 c01010e8 00000000 00000000 00000000 00000000
> > > > >     1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > > >     1fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
> > > > >     [<c08533ec>] (dsa_switch_event) from [<c014bdfc>] (notifier_call_chain+0x48/0x84)
> > > > >     [<c014bdfc>] (notifier_call_chain) from [<c014bef0>] (raw_notifier_call_chain+0x18/0x20)
> > > > >     [<c014bef0>] (raw_notifier_call_chain) from [<c08509a8>] (dsa_port_mdb_add+0x48/0x74)
> > > > >     [<c08509a8>] (dsa_port_mdb_add) from [<c087e248>] (__switchdev_handle_port_obj_add+0x54/0xd4)
> > > > >     [<c087e248>] (__switchdev_handle_port_obj_add) from [<c087e2d0>] (switchdev_handle_port_obj_add+0x8/0x14)
> > > > >     [<c087e2d0>] (switchdev_handle_port_obj_add) from [<c08523c4>] (dsa_slave_switchdev_blocking_event+0x94/0xa4)
> > > > >     [<c08523c4>] (dsa_slave_switchdev_blocking_event) from [<c014bdfc>] (notifier_call_chain+0x48/0x84)
> > > > >     [<c014bdfc>] (notifier_call_chain) from [<c014c500>] (blocking_notifier_call_chain+0x50/0x68)
> > > > >     [<c014c500>] (blocking_notifier_call_chain) from [<c087dfb4>] (switchdev_port_obj_notify+0x44/0xa8)
> > > > >     [<c087dfb4>] (switchdev_port_obj_notify) from [<c087e0a8>] (switchdev_port_obj_add_now+0x90/0x104)
> > > > >     [<c087e0a8>] (switchdev_port_obj_add_now) from [<c087e130>] (switchdev_port_obj_add_deferred+0x14/0x5c)
> > > > >     [<c087e130>] (switchdev_port_obj_add_deferred) from [<c087de4c>] (switchdev_deferred_process+0x64/0x104)
> > > > >     [<c087de4c>] (switchdev_deferred_process) from [<c087def8>] (switchdev_deferred_process_work+0xc/0x14)
> > > > >     [<c087def8>] (switchdev_deferred_process_work) from [<c01447dc>] (process_one_work+0x218/0x50c)
> > > > >     [<c01447dc>] (process_one_work) from [<c0145b84>] (worker_thread+0x44/0x5bc)
> > > > >     [<c0145b84>] (worker_thread) from [<c014a6f8>] (kthread+0x148/0x150)
> > > > >     [<c014a6f8>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
> > > > >     Exception stack(0xee871fb0 to 0xee871ff8)
> > > > >     1fa0:                                     00000000 00000000 00000000 00000000
> > > > >     1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> > > > >     1fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> > > > >     Code: bad PC value
> > > > >     ---[ end trace 1292c61abd17b130 ]---
> > > > >
> > > > >     [<c08533ec>] (dsa_switch_event) from [<c014bdfc>] (notifier_call_chain+0x48/0x84)
> > > > >     corresponds to
> > > > >
> > > > >       $ arm-linux-gnueabihf-addr2line -C -i -e vmlinux c08533ec
> > > > >
> > > > >       linux/net/dsa/switch.c:156
> > > > >       linux/net/dsa/switch.c:178
> > > > >       linux/net/dsa/switch.c:328
> > > > >
> > > > > Fixes: e6db98db8a95 ("net: dsa: add switch mdb bitmap functions")
> > > > > Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> > > > > ---
> > > > > Changes since v1:
> > > > >
> > > > >   - Moved the check to the beginning of dsa_switch_mdb_add()
> > > > >
> > > > > Looks like we could also move the ops check out of
> > > > > dsa_switch_mdb_prepare_bitmap(), though I suppose keeping the code the
> > > > > way it is now is clearer.
> > > > >
> > > > > ---
> > > > >  net/dsa/switch.c | 3 +++
> > > > >  1 file changed, 3 insertions(+)
> > > > >
> > > > > diff --git a/net/dsa/switch.c b/net/dsa/switch.c
> > > > > index 4ec5b7f85d51..231af5268656 100644
> > > > > --- a/net/dsa/switch.c
> > > > > +++ b/net/dsa/switch.c
> > > > > @@ -164,6 +164,9 @@ static int dsa_switch_mdb_add(struct dsa_switch *ds,
> > > > >       struct switchdev_trans *trans = info->trans;
> > > > >       int port;
> > > > >
> > > > > +     if (!ds->ops->port_mdb_add)
> > > > > +             return -EOPNOTSUPP;
> > > > > +
> > > > >       /* Build a mask of Multicast group members */
> > > > >       bitmap_zero(ds->bitmap, ds->num_ports);
> > > > >       if (ds->index == info->sw_index)
> > > > > --
> > > > > 2.20.1
> > > > >
> > > >
> > > > I don't understand the crash here, nor the fix. dsa_switch_mdb_add()
> > > > is supposed to be called through switchdev with a prepare phase,
> > > > which checks for ds->ops->port_mdb_add. Do you mean that a switchdev
> > > > MDB object is added somewhere without a prepare phase? If that's
> > > > the case, this is what the commit message must say. Then the
> > >
> > > I had pretty much zero understanding of how switchdev and dsa work.
> > > The symptom is a NULL pointer reference, resulting from an unsupported
> > > callback that was not checked before being called, as described above.
> > > And that is what I mean. A NULL pointer reference happened when it
> > > should not have.
> > >
> > > Based on what you just mentioned, yes it does look like an object was
> > > added without a prepare phase. Randomly looking through the net/dsa
> > > code, it seems only dsa_port_vid_add() does a prepare phase, judging
> > > by .ph_prepare being set. dsa_port_{vlan,mbd,fdb}_add directly call
> > > the add phase, without the prepare phase. So I'm guessing "supposed
> > > to be called with a prepare phase" is not quite accurate. This also
> > > exceeds the scope of the simple fix I had in mind.
> > >
> > > > ds->ops->port_mdb_add check must go where it is used, that is to say
> > > > at the beginning of dsa_switch_mdb_add_bitmap() (similarly to what
> > > > dsa_switch_mdb_prepare_bitmap() does), not in dsa_switch_mdb_add.
> > >
> > > Andrew asked me to move it to where it is now. Please take a look at
> > > v1 [2] if it's what you would like.
> > >
> > > I'm ok either way.
> >
> > I still cannot find in the code where a SWITCHDEV_OBJ_ID_PORT_MDB object
> > gets added without a prepare phase or a trans object, but it wouldn't hurt to
> > double check the presence of ds->ops->port_mdb_add before calling it anyway,
> > since a patch may actually bypass this prepare phase.
> 
> I dug a bit more and I couldn't find it either. AFAICS the only place it
> gets called is through the notification chain invoked in
> switchdev_port_obj_add_now(),
> which specifically has prepare and commit phases.
> 
> > Your v1 patch was a bit confusing and changed the signature of the function
> > at the same time. Please check the callback where it is used, like this:
> >
> >     diff --git a/net/dsa/switch.c b/net/dsa/switch.c
> >     index 4ec5b7f85d51..09d9286b27cc 100644
> >     --- a/net/dsa/switch.c
> >     +++ b/net/dsa/switch.c
> >     @@ -153,6 +153,9 @@ static void dsa_switch_mdb_add_bitmap(struct dsa_switch *ds,
> >      {
> >             int port;
> >
> >     +       if (!ds->ops->port_mdb_add)
> >     +               return;
> >     +
> >             for_each_set_bit(port, bitmap, ds->num_ports)
> >                     ds->ops->port_mdb_add(ds, port, mdb);
> >      }
> >
> >
> > This will be easier to maintain. Please provide a simpler commit message,
> 
> OK. How about:
> 
> The dsa framework has optional .port_mdb_{prepare,add,delete} callback fields

s/delete/del/

> for drivers to handle multicast database entries. When adding an entry, the
> framework goes through a prepare phase, then a commit phase. Drivers not
> providing these callbacks should be detected in the prepare phase.
> 
> For some unknown reason, the guard in the prepare phase is insufficient,

I'd change the line above with something like:

    DSA core may still bypass the bridge layer and call the dsa_port_mdb_add
    function directly with no prepare phase or no switchdev trans object,

> and the framework ends up calling an undefined .port_mdb_add callback.
> This results in a NULL pointer dereference, as shown in the log below.

But yes you get the idea right ;-)

> Add a check for .port_mdb_add before calling it in dsa_switch_mdb_add_bitmap().
> 
> <attach log>
> 
> > this one is not relevant. Are you actually able to reproduce this stack
> > trace? If not, that is not necessary to add it to the commit message...
> 
> Yes I can reproduce it. Just did on a vanilla v5.3-rc3 kernel.
> 
> [   71.827837] br0: port 1(eth0.1) entered blocking state
> [   71.844072] br0: port 1(eth0.1) entered disabled state
> [   71.849669] device eth0.1 entered promiscuous mode
> [   71.865848] device eth0 entered promiscuous mode
> [   71.876535] br0: port 2(wan) entered blocking state
> [   71.881475] br0: port 2(wan) entered disabled state
> [   71.888631] device wan entered promiscuous mode
> [   71.914341] bcm53xx stmmac-0:1e wan: configuring for phy/gmii link mode
> [   71.921505] 8021q: adding VLAN 0 to HW filter on device wan
> [   71.930146] bcm53xx stmmac-0:1e wan: Link is Up - 1Gbps/Full - flow
> control rx/tx
> [   71.932360] br0: port 3(lan1) entered blocking state
> [   71.942751] br0: port 3(lan1) entered disabled state
> [   71.950128] device lan1 entered promiscuous mode
> [   71.970024] bcm53xx stmmac-0:1e lan1: configuring for phy/gmii link mode
> [   71.977157] 8021q: adding VLAN 0 to HW filter on device lan1
> [   71.988159] br0: port 4(lan2) entered blocking state
> [   71.993158] br0: port 4(lan2) entered disabled state
> [   72.001235] device lan2 entered promiscuous mode
> [   72.020994] bcm53xx stmmac-0:1e lan2: configuring for phy/gmii link mode
> [   72.028081] 8021q: adding VLAN 0 to HW filter on device lan2
> [   72.035797] bcm53xx stmmac-0:1e lan2: Link is Up - 1Gbps/Full -
> flow control rx/tx
> [   72.038767] br0: port 5(lan3) entered blocking state
> [   72.048450] br0: port 5(lan3) entered disabled state
> [   72.057129] device lan3 entered promiscuous mode
> [   72.076956] bcm53xx stmmac-0:1e lan3: configuring for phy/gmii link mode
> [   72.084004] 8021q: adding VLAN 0 to HW filter on device lan3
> [   72.091352] bcm53xx stmmac-0:1e lan3: Link is Up - 1Gbps/Full -
> flow control rx/tx
> [   72.095168] br0: port 6(lan4) entered blocking state
> [   72.103926] br0: port 6(lan4) entered disabled state
> [   72.113313] device lan4 entered promiscuous mode
> [   72.133293] bcm53xx stmmac-0:1e lan4: configuring for phy/gmii link mode
> [   72.140410] 8021q: adding VLAN 0 to HW filter on device lan4
> [   72.147682] bcm53xx stmmac-0:1e lan4: Link is Up - 100Mbps/Full -
> flow control rx/tx
> [   72.155915] br0: port 6(lan4) entered blocking state
> [   72.160905] br0: port 6(lan4) entered forwarding state
> [   72.166135] br0: port 5(lan3) entered blocking state
> [   72.171111] br0: port 5(lan3) entered forwarding state
> [   72.176300] br0: port 4(lan2) entered blocking state
> [   72.181277] br0: port 4(lan2) entered forwarding state
> [   72.186472] br0: port 2(wan) entered blocking state
> [   72.191361] br0: port 2(wan) entered forwarding state
> [   72.196453] br0: port 1(eth0.1) entered blocking state
> [   72.201601] br0: port 1(eth0.1) entered forwarding state
> 
> Waiting for br0 to get ready (MAXWAIT is 32 seconds).
> [   72.244956] 8<--- cut here ---
> [   72.248072] Unable to handle kernel NULL pointer dereference at
> virtual address 00000000
> [   72.256331] pgd = (ptrval)
> [   72.259048] [00000000] *pgd=00000000
> [   72.262642] Internal error: Oops: 80000005 [#1] SMP ARM
> [   72.267869] Modules linked in:
> [   72.270934] CPU: 1 PID: 134 Comm: kworker/1:2 Not tainted 5.3.0-rc3 #1
> [   72.277458] Hardware name: Allwinner sun7i (A20) Family
> [   72.282699] Workqueue: events switchdev_deferred_process_work
> [   72.288447] PC is at 0x0
> [   72.290988] LR is at dsa_switch_event+0x570/0x620
> [   72.295691] pc : [<00000000>]    lr : [<c0853890>]    psr: 80070113
> [   72.301955] sp : ef3cfdb8  ip : 00000000  fp : ef0ad0a4
> [   72.307180] r10: 0000000c  r9 : 00000008  r8 : eeb3b450
> [   72.312405] r7 : ef0ad040  r6 : ef0ad088  r5 : c0f04c48  r4 : ef0ad04c
> [   72.318931] r3 : 00000000  r2 : eeb3b450  r1 : 00000008  r0 : ef0ad040
> [   72.325459] Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> [   72.332593] Control: 10c5387d  Table: 6de6406a  DAC: 00000051
> [   72.338340] Process kworker/1:2 (pid: 134, stack limit = 0x(ptrval))
> [   72.344692] Stack: (0xef3cfdb8 to 0xef3d0000)
> [   72.349085] fda0:
>     ef3cfe14 46893f30
> [   72.357329] fdc0: 00000000 ffffffff 00000000 ef3cfe14 00000005
> 00000000 c0852944 00000000
> [   72.365550] fde0: ffffe000 c014be24 c0f04c48 ef3cfe98 c0f04c48
> ee9ea800 c08515d8 c014bf18
> [   72.373739] fe00: 00000000 63a7c876 ee9b0068 c0850e60 ef26e800
> eeb3b450 ef3cfecb 00000000
> [   72.381921] fe20: 00000008 46893f30 00000000 c087e718 eebe2068
> 46893f30 c0e72400 ffffffff
> [   72.390102] fe40: 00000000 ef3cfe98 00000006 00000000 c0fb2a50
> c087e7a0 ffffffff c0852868
> [   72.398283] fe60: ffffffff c014be24 00000006 c0fad2d0 ef3cfe98
> eeb3b450 00000000 c014c528
> [   72.406463] fe80: 00000000 c015dcf8 c0f04c48 00000000 ee9ea800
> c087e484 ee9ea800 00000000
> [   72.414644] fea0: eeb3b450 ef3cfecb 00000001 46893f30 00000000
> c0f04c48 00000000 c087e578
> [   72.422825] fec0: 00000000 ef26e780 00024400 46893f30 eeb3b440
> eeb3b450 ee9ea800 00000122
> [   72.430998] fee0: 00000100 c087e600 eeb3b440 c0fad2c8 c1003ef0
> c087e31c 2e928000 c0fad2ec
> [   72.439179] ff00: c0fad2ec ee858080 ef7a62c0 ef7a9400 00000000
> c087e3c8 c0fad2ec c0144804
> [   72.447360] ff20: ef312280 ef7a62c0 00000008 ee858080 ee858094
> ef7a62c0 00000008 c0f03d00
> [   72.455541] ff40: ef7a62d8 ef7a62c0 ffffe000 c0145bac ffffe000
> c0fb2420 c0bfa1ec 00000000
> [   72.463721] ff60: ffffe000 ee855c40 ee855c00 00000000 ef3ce000
> ee858080 c0145b68 ef0e5ea4
> [   72.471902] ff80: ee855c5c c014a720 0000000b ee855c00 c014a5d8
> 00000000 00000000 00000000
> [   72.480082] ffa0: 00000000 00000000 00000000 c01010e8 00000000
> 00000000 00000000 00000000
> [   72.488262] ffc0: 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000
> [   72.496442] ffe0: 00000000 00000000 00000000 00000000 00000013
> 00000000 00000000 00000000
> [   72.504652] [<c0853890>] (dsa_switch_event) from [<c014be24>]
> (notifier_call_chain+0x48/0x84)
> [   72.513184] [<c014be24>] (notifier_call_chain) from [<c014bf18>]
> (raw_notifier_call_chain+0x18/0x20)
> [   72.522321] [<c014bf18>] (raw_notifier_call_chain) from
> [<c0850e60>] (dsa_port_mdb_add+0x48/0x74)
> [   72.531200] [<c0850e60>] (dsa_port_mdb_add) from [<c087e718>]
> (__switchdev_handle_port_obj_add+0x54/0xd4)
> [   72.540773] [<c087e718>] (__switchdev_handle_port_obj_add) from
> [<c087e7a0>] (switchdev_handle_port_obj_add+0x8/0x14)
> [   72.551385] [<c087e7a0>] (switchdev_handle_port_obj_add) from
> [<c0852868>] (dsa_slave_switchdev_blocking_event+0x94/0xa4)
> [   72.562343] [<c0852868>] (dsa_slave_switchdev_blocking_event) from
> [<c014be24>] (notifier_call_chain+0x48/0x84)
> [   72.572434] [<c014be24>] (notifier_call_chain) from [<c014c528>]
> (blocking_notifier_call_chain+0x50/0x68)
> [   72.582004] [<c014c528>] (blocking_notifier_call_chain) from
> [<c087e484>] (switchdev_port_obj_notify+0x44/0xa8)
> [   72.592094] [<c087e484>] (switchdev_port_obj_notify) from
> [<c087e578>] (switchdev_port_obj_add_now+0x90/0x104)
> [   72.602098] [<c087e578>] (switchdev_port_obj_add_now) from
> [<c087e600>] (switchdev_port_obj_add_deferred+0x14/0x5c)
> [   72.612537] [<c087e600>] (switchdev_port_obj_add_deferred) from
> [<c087e31c>] (switchdev_deferred_process+0x64/0x104)
> [   72.623060] [<c087e31c>] (switchdev_deferred_process) from
> [<c087e3c8>] (switchdev_deferred_process_work+0xc/0x14)
> [   72.633412] [<c087e3c8>] (switchdev_deferred_process_work) from
> [<c0144804>] (process_one_work+0x218/0x50c)
> [   72.643156] [<c0144804>] (process_one_work) from [<c0145bac>]
> (worker_thread+0x44/0x5bc)
> [   72.651253] [<c0145bac>] (worker_thread) from [<c014a720>]
> (kthread+0x148/0x150)
> [   72.658657] [<c014a720>] (kthread) from [<c01010e8>]
> (ret_from_fork+0x14/0x2c)
> [   72.665879] Exception stack(0xef3cffb0 to 0xef3cfff8)
> [   72.670932] ffa0:                                     00000000
> 00000000 00000000 00000000
> [   72.679112] ffc0: 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000
> [   72.687291] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [   72.693911] Code: bad PC value
> [   72.697022] ---[ end trace c7626868564873c8 ]---

Good to know!


Thank you,

	Vivien

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