WARNING in canfd_rcv

[syzbot]

Hello,

syzkaller hit the following crash on
ce3c209f6733e2cff9335bb1b2ac847fa823410a
git://git.cmpxchg.org/linux-mmots.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+e3b775...@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.

PF_CAN: dropped non conform CAN FD skbuf: dev type 65534, len 128, datalen 0
WARNING: CPU: 0 PID: 3661 at net/can/af_can.c:750 canfd_rcv+0x1c5/0x200
net/can/af_can.c:745
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3661 Comm: syzkaller656999 Not tainted 4.15.0-rc7-mm1+ #56
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
panic+0x1e4/0x41c kernel/panic.c:183
__warn+0x1dc/0x200 kernel/panic.c:547
report_bug+0x211/0x2d0 lib/bug.c:184
fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
fixup_bug arch/x86/kernel/traps.c:247 [inline]
do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1085
RIP: 0010:canfd_rcv+0x1c5/0x200 net/can/af_can.c:745
RSP: 0018:ffff8801d9bdf028 EFLAGS: 00010286
RAX: dffffc0000000008 RBX: ffff8801d99fd800 RCX: ffffffff815a58fe
RDX: 0000000000000000 RSI: ffff8801bcf44c38 RDI: 0000000000000293
RBP: ffff8801d9bdf050 R08: 0000000000000000 R09: 0000000000000000
R10: ffff8801d9bdf570 R11: 0000000000000000 R12: ffff8801bc5a8340
R13: ffff8801d99fc600 R14: 000000000000fffe R15: ffffffff87055040
__netif_receive_skb_core+0x1a41/0x3460 net/core/dev.c:4538
__netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4603
netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4677
netif_receive_skb+0xae/0x390 net/core/dev.c:4701
tun_rx_batched.isra.51+0x5ee/0x870 drivers/net/tun.c:1524
tun_get_user+0x25de/0x3940 drivers/net/tun.c:1924
tun_chr_write_iter+0xb9/0x160 drivers/net/tun.c:1952
call_write_iter include/linux/fs.h:1775 [inline]
new_sync_write fs/read_write.c:469 [inline]
__vfs_write+0x684/0x970 fs/read_write.c:482
vfs_write+0x189/0x510 fs/read_write.c:544
SYSC_write fs/read_write.c:589 [inline]
SyS_write+0xef/0x220 fs/read_write.c:581
entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x444b49
RSP: 002b:00000000007eff38 EFLAGS: 00000297 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 0000000000444b49
RDX: 0000000000000084 RSI: 0000000020ab08cd RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000402740
R13: 00000000004027d0 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzk...@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug
report.
Note: all commands must start from beginning of the line in the email body.