Messages in this thread | | | Date | Tue, 18 Jan 2022 15:44:13 +0100 | Subject | Re: [PATCH net] can: isotp: isotp_rcv_cf(): fix so->rx race problem | From | Oliver Hartkopp <> |
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On 18.01.22 13:46, Ziyang Xuan (William) wrote: >> Hi, >> >> the referenced syzbot issue has already been fixed in upstream here: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=5f33a09e769a9da0482f20a6770a342842443776 >> >> ("can: isotp: convert struct tpcon::{idx,len} to unsigned int") >> >> Additionally this fix changes some behaviour that is required by the ISO 16765-2 specification (see below). >> >> On 17.01.22 13:01, Ziyang Xuan wrote: >>> When receive a FF, the current code logic does not consider the real >>> so->rx.state but set so->rx.state to ISOTP_IDLE directly. That will >>> make so->rx accessed by multiple receiving processes concurrently. >> >> This is intentionally. "multiple receiving processes" are not allowed resp. specified by ISO 15765-2. > > Does it can be a network attack?
Yes. You can see it like this. The ISO 15765-2 protocol is an unreliable UDP-like datagram protocol and the session layer takes care about timeouts and packet lost.
If you want to disturb that protocol you can also send PDUs with out-of-sync packet counters which will make the receiver drop the communication attempt.
This is 'CAN-style' ... as usually the bus is very reliable. Security and reliable communication is done on top of these protocols.
> It receives packets from network, but unexpected packets order make server panic.
Haha, no :-)
Unexpected packets should not make the server panic but only drop the communication process.
In the case pointed out by syzbot the unsigned 32 bit length information was stored in a signed 32 bit integer which caused a sanity check to fail.
This is now fixed with the patch from Marc.
Regards, Oliver
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