Re: kernel page fault in r8712u

[Larry Finger <Larry.Finger@lwfinger.net>]

On 05/16/2015 12:16 PM, Haggai Eran wrote:
> On 16 May 2015 at 17:57, Larry Finger <Larry.Finger@lwfinger.net> wrote:
>> The problem appears to be from r8712u. From the stack dump, the problem
>> happens when r8712_free_recvframe() calls __dev_kfree_skb_any(). A
>> complication is that my copy of the kernel source does not show such a call.
>> :(
>>
>> Please use gdb to help with the debugging. From the main directory of your
>> source, enter the command 'gdb drivers/staging/rtl8712/r8712u.ko'. Once it
>> prompts you, enter 'l *r8712_free_recvframe+0x2c'. The first character is
>> ell, not one. That will show the actual line of code. Please post that info.
>
> Here's what I get:
>
> (gdb) l *r8712_free_recvframe+0x2c
> 0x16714 is in r8712_free_recvframe (drivers/staging/rtl8712/rtl8712_recv.c:145).
> 140             struct _adapter *padapter = precvframe->u.hdr.adapter;
> 141             struct recv_priv *precvpriv = &padapter->recvpriv;
> 142
> 143             if (precvframe->u.hdr.pkt) {
> 144
> dev_kfree_skb_any(precvframe->u.hdr.pkt);/*free skb by driver*/
> 145                     precvframe->u.hdr.pkt = NULL;
> 146             }
> 147             spin_lock_irqsave(&pfree_recv_queue->lock, irqL);
> 148             list_del_init(&(precvframe->u.hdr.list));
> 149             list_add_tail(&(precvframe->u.hdr.list),
> &pfree_recv_queue->queue);
>
> It seems that dev_kfree_skb_any is an inline function that calls
> __dev_kfree_skb_any,
> so that should explain why that call didn't show up in the stack dump.

Thanks. From your original posting, the bad address for precvframe->u.hdr.pkt is 
a9d797d7. I'm a little bothered by that odd address. I would have expected it to 
be even, at least. The actual definition should be OK with the alignment, but 
there are a number of places where there is a cast. If the alignment of the 
object of the cast is wrong, then that might cause the problem. It will take a 
while to trace back through your call chain to see if any of these are involved 
here.

I will be back to you later.

Larry