Re: [PATCH v2 net] net: dsa: fix panic when removing unoffloaded port from bridge

[Vladimir Oltean]

On Mon, Feb 21, 2022 at 09:35:38PM +0100, Alvin Šipraga wrote:
> From: Alvin Šipraga <alsi@xxxxxxxxxxxxxxx>
> 
> 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: d3eed0e57d5d ("net: dsa: keep the bridge_dev and bridge_num as part of the same structure")
> Signed-off-by: Alvin Šipraga <alsi@xxxxxxxxxxxxxxx>
> ---

Reviewed-by: Vladimir Oltean <olteanv@xxxxxxxxx>