netdev - Re: [PATCH RFC v2 1/2] can: fix multiple delivery of a single CAN frame for overlapping CAN filters

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <55192280.8090505@pengutronix.de>
Date:	Mon, 30 Mar 2015 12:16:32 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Oliver Hartkopp <socketcan@...tkopp.net>, linux-can@...r.kernel.org
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH RFC v2 1/2] can: fix multiple delivery of a single
 CAN frame for overlapping CAN filters

On 03/30/2015 12:10 PM, Marc Kleine-Budde wrote:
> On 03/29/2015 08:09 PM, Oliver Hartkopp wrote:
>> The CAN_RAW socket can set multiple CAN identifier specific filters that lead
>> to multiple filters in the af_can.c filter processing. These filters are
>> indenpendent from each other which leads to logical OR'ed filters when applied.
       ^
independent

>> This patch makes sure that every CAN frame which is filtered for a specific
>> socket is only delivered once to the user space. This is independent from the
>> number of matching CAN filters of this socket.
>>
>> As the can_raw() function is executed from NET_RX softirq the introduced
>> variables are implemented as per-CPU variables to avoid extensive locking at
>> CAN frame reception time.
>>
>> Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>

>> +	/* eliminate multiple filter matches for the same skb */
>> +	if (*this_cpu_ptr(ro->uniq_skb) == oskb &&
>> +	    ktime_equal(*this_cpu_ptr(ro->uniq_tstamp), oskb->tstamp)) {
>> +			return;
>> +	} else {
>> +		*this_cpu_ptr(ro->uniq_skb) = oskb;
>> +		*this_cpu_ptr(ro->uniq_tstamp) = oskb->tstamp;
>> +	}
>> +
> 
> What happens if you're preempted somewhere in this code, it's not
> atomic? I think, if we only have to take care about the skb, an atomic
> compare exchange would work. But we have two variables....If you use a
> struct (see previous mail), I think the usage of get_cpu_ptr(),
> git_cpu_ptr() ensures that we're not preempted.
  ^^^^^^^^^^^^^
put_cpu_ptr()

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


Download attachment "signature.asc" of type "application/pgp-signature" (820 bytes)