On Mon, 2017-03-13 at 13:47 +0100, Petr Vorel wrote:
> commit 7489bdadb7d1 (r8152: check rx after napi is enabled) causes null
> pointer dereference when using device as under root:
>
> # rmmod r8152 # or lsusb -v
> NOHZ: local_softirq_pending 08
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> IP: r8152_poll+0x125/0x570 [r8152]
> PGD 89b4cf067
> PUD 898ff2067
> PMD 0
> Oops: 0002 [#1] PREEMPT SMP
>
> Signed-off-by: Petr Vorel <petr.vo...@gmail.com>
> ---
> NOTE: This is just a workaround, I suppose, there is better way how to fix
> that
> (which allows keeping scheduling the napi for rx after napi_enable()).
> ---
> drivers/net/usb/r8152.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index 986243c932cc..79c665a89a47 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -3703,8 +3703,6 @@ static int rtl8152_resume(struct usb_interface *intf)
> napi_enable(&tp->napi);
> clear_bit(SELECTIVE_SUSPEND, &tp->flags);
> smp_mb__after_atomic();
> - if (!list_empty(&tp->rx_done))
> - napi_schedule(&tp->napi);
> } else {
> tp->rtl_ops.up(tp);
> netif_carrier_off(tp->netdev);
The proper work around is to enclose the napi_schedule() in a
local_bh_enable()/local_bh_disable() pair.
