If a bridged port is not offloaded to the hardware - either because the
underlying driver does not implement the port_bridge_{join,leave} ops,
or because the operation failed - then its dp->bridge pointer will be
NULL when dsa_port_bridge_leave() is called. Avoid dereferncing NULL.
This fixes the following splat when removing a port from a bridge:
Unable to handle kernel access to user memory outside uaccess routines at virtual address 0000000000000000
Internal error: Oops: 96000004 [#1] PREEMPT_RT SMP
CPU: 3 PID: 1119 Comm: brctl Tainted: G O 5.17.0-rc4-rt4 #1
Call trace:
dsa_port_bridge_leave+0x8c/0x1e4
dsa_slave_changeupper+0x40/0x170
dsa_slave_netdevice_event+0x494/0x4d4
notifier_call_chain+0x80/0xe0
raw_notifier_call_chain+0x1c/0x24
call_netdevice_notifiers_info+0x5c/0xac
__netdev_upper_dev_unlink+0xa4/0x200
netdev_upper_dev_unlink+0x38/0x60
del_nbp+0x1b0/0x300
br_del_if+0x38/0x114
add_del_if+0x60/0xa0
br_ioctl_stub+0x128/0x2dc
br_ioctl_call+0x68/0xb0
dev_ifsioc+0x390/0x554
dev_ioctl+0x128/0x400
sock_do_ioctl+0xb4/0xf4
sock_ioctl+0x12c/0x4e0
__arm64_sys_ioctl+0xa8/0xf0
invoke_syscall+0x4c/0x110
el0_svc_common.constprop.0+0x48/0xf0
do_el0_svc+0x28/0x84
el0_svc+0x1c/0x50
el0t_64_sync_handler+0xa8/0xb0
el0t_64_sync+0x17c/0x180
Code: f9402f00 f0002261 f9401302 913cc021 (a9401404)
---[ end trace 0000000000000000 ]---
Fixes: d3eed0e57d ("net: dsa: keep the bridge_dev and bridge_num as part of the same structure")
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220221203539.310690-1-alvin@pqrs.dk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
342b641919