Subject: Re: [PATCH][AX25] ax25_out: check skb for NULL in ax25_kick()

From: Pidoux <[email-masked]>
Date: Sun, 09 Mar 2008 10:02:39 +0100

Jann Traschewski a écrit :
> Applied and stable with Kernel 2.6.24.2 since 12 hours.
> Regards,
> Jann
>
>   
>> -----Ursprüngliche Nachricht-----
>> Von: Jarek Poplawski [mailto:[email-masked]] 
>> Gesendet: Mittwoch, 13. Februar 2008 12:56
>> An: David Miller
>> Cc: Jann Traschewski; Bernard Pidoux F6BVP; Ralf Baechle; 
>> [email-masked]
>> Betreff: [PATCH][AX25] ax25_out: check skb for NULL in ax25_kick()
>>
>> Hi,
>>
>> Here is an "official" version of "testing patch #2" from this thread.
>> The only difference: ax25->vs is changed only after checking 
>> skb is not NULL (plus a comment). IMHO it could be applied.
>>
>> Thanks,
>> Jarek P.
>>
>> ---------------->
>>
>> Subject: [AX25] ax25_out: check skb for NULL in ax25_kick()
>>
>> According to some OOPS reports ax25_kick tries to clone NULL 
>> skbs sometimes. It looks like a race with 
>> ax25_clear_queues(). Probably there is no need to add more 
>> than a simple check for this yet.
>> Another report suggested there are probably also cases where ax25
>> ->paclen == 0 can happen in ax25_output(); this wasn't confirmed
>> during testing but let's leave this debugging check for some time.
>>
>>
>> Reported-and-tested-by: Jann Traschewski <[email-masked]>
>> Signed-off-by: Jarek Poplawski <[email-masked]>
>>
>> ---
>>
>> diff -Nurp 2.6.24-mm1-/net/ax25/ax25_out.c 
>> 2.6.24-mm1+/net/ax25/ax25_out.c
>> --- 2.6.24-mm1-/net/ax25/ax25_out.c	2008-01-24 
>> 22:58:37.000000000 +0000
>> +++ 2.6.24-mm1+/net/ax25/ax25_out.c	2008-02-13 
>> 10:43:50.000000000 +0000
>> @@ -117,6 +117,12 @@ void ax25_output(ax25_cb *ax25, int pacl
>>  	unsigned char *p;
>>  	int frontlen, len, fragno, ka9qfrag, first = 1;
>>  
>> +	if (paclen < 16) {
>> +		WARN_ON_ONCE(1);
>> +		kfree_skb(skb);
>> +		return;
>> +	}
>> +
>>  	if ((skb->len - 1) > paclen) {
>>  		if (*skb->data == AX25_P_TEXT) {
>>  			skb_pull(skb, 1); /* skip PID */
>> @@ -251,8 +257,6 @@ void ax25_kick(ax25_cb *ax25)
>>  	if (start == end)
>>  		return;
>>  
>> -	ax25->vs = start;
>> -
>>  	/*
>>  	 * Transmit data until either we're out of data to send or
>>  	 * the window is full. Send a poll on the final I frame 
>> if @@ -261,8 +265,13 @@ void ax25_kick(ax25_cb *ax25)
>>  
>>  	/*
>>  	 * Dequeue the frame and copy it.
>> +	 * Check for race with ax25_clear_queues().
>>  	 */
>>  	skb  = skb_dequeue(&ax25->write_queue);
>> +	if (!skb)
>> +		return;
>> +
>> +	ax25->vs = start;
>>  
>>  	do {
>>  		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
>>     
>
>
>
>   
Applied too and stable with kernel 2.6.24.3 since a week.

Thanks Jarek.

Bernard Pidoux