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 <m...@pengutronix.de> > > 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: syzbot+4386709c0c1284dca...@syzkaller.appspotmail.com > > > > It will help syzbot understand when the bug is fixed. See footer for > > > > details. > > > > If you forward the report, please keep this part and the footer. > > > > > > > > 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. Eric
