On 01/17/2018 08:12 AM, Eric Biggers wrote:
On Wed, Jan 17, 2018 at 07:39:24AM +0100, Oliver Hartkopp wrote:
On 01/16/2018 07:11 PM, Dmitry Vyukov wrote:
On Tue, Jan 16, 2018 at 7:07 PM, Marc Kleine-Budde <[email protected]> wrote:
On 01/16/2018 06:58 PM, syzbot wrote:
Hello,
syzkaller hit the following crash on
a8750ddca918032d6349adbf9a4b6555e7db20da
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email protected]
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device eql entered promiscuous mode
------------[ cut here ]------------
PF_CAN: dropped non conform CAN skbuf: dev type 65534, len 42, datalen 0
WARNING: CPU: 0 PID: 3650 at net/can/af_can.c:729 can_rcv+0x1c5/0x200
net/can/af_can.c:724
Kernel panic - not syncing: panic_on_warn set ...
Invalid packages generate a warning (WARN_ONCE()), and you have
panic_on_warn active. Should we better silently drop these CAN packages?
Hi,
pr_warn_once() will be more appropriate. It prints a single line.
The idea behind this WARN() is to detect really bad things that might have
happen on network driver level:
The CAN subsystem registers with dev_add_pack() for ETH_P_CAN and
ETH_P_CANFD only. These ETH_P_ types are only allowed to be created by CAN
network devices (like vcan, vxcan, and real CAN drivers).
I don't have any strong opinion on using WARN() or pr_warn_once().
Is this detected violation worth using WARN(), as something already must
have gone really wrong to trigger this issue?
WARN() indicates a kernel bug. If it's instead "userspace did something
stupid", or "someone sent some unexpected network packet", it needs to be
pr_warn_once(), pr_warn_ratelimited(), or removed entirely.
Ok. Thanks for the explanation!
It is "some bogus network driver sent something unexpected" - but that
does not harm the entire system.
pr_warn_once() seems the right way to go then.
Thanks,
Oliver
