kernel BUG at net/l2tp/l2tp_ppp.c:LINE!

[syzbot]

Hello,

syzkaller hit the following crash on
73005e1a35fd67c644b0645c9e4c1efabd0fe62c
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output 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+114b15...@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.

------------[ cut here ]------------
kernel BUG at net/l2tp/l2tp_ppp.c:176!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3550 Comm: syz-executor3 Not tainted 4.15.0-rc6-next-20180103+
#87
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:pppol2tp_sock_to_session net/l2tp/l2tp_ppp.c:176 [inline]
RIP: 0010:pppol2tp_sendmsg+0x4fd/0x660 net/l2tp/l2tp_ppp.c:304
RSP: 0018:ffff8801d007f9a0 EFLAGS: 00010293
RAX: ffff8801d0074180 RBX: ffff8801bf4a8ec0 RCX: ffffffff8473da1d
RDX: 0000000000000000 RSI: ffff8801d007fdb0 RDI: ffff8801bf4a92a0
RBP: ffff8801d007fa10 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000003 R11: ffffed003a00feff R12: ffff8801c0e4ab40
R13: 0000000000000000 R14: 00000000000000ec R15: ffff8801ba8fc680
FS: 00007f7a046ca700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004d5878 CR3: 00000001bf7c8005 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
sock_sendmsg_nosec net/socket.c:628 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:638
___sys_sendmsg+0x2f4/0x8c0 net/socket.c:2018
__sys_sendmmsg+0x159/0x3c0 net/socket.c:2108
SYSC_sendmmsg net/socket.c:2139 [inline]
SyS_sendmmsg+0x35/0x60 net/socket.c:2134
entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x452ac9
RSP: 002b:00007f7a046c9c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 000000000071c010 RCX: 0000000000452ac9
RDX: 0000000000000001 RSI: 0000000020003fc8 RDI: 0000000000000000
RBP: 0000000000000465 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f4a18
R13: 00000000ffffffff R14: 00007f7a046ca6d4 R15: 0000000000000006
Code: 0a 35 ea fc 48 8b 7d d0 e8 b1 41 aa fd 84 c0 74 0d e8 f8 34 ea fc 48
89 df e8 60 35 50 ff 41 bd f7 ff ff ff eb 86 e8 e3 34 ea fc <0f> 0b 41 bd
95 ff ff ff e9 74 ff ff ff e8 61 16 16 fd e9 8c fb
RIP: pppol2tp_sock_to_session net/l2tp/l2tp_ppp.c:176 [inline] RSP:
ffff8801d007f9a0
RIP: pppol2tp_sendmsg+0x4fd/0x660 net/l2tp/l2tp_ppp.c:304 RSP:
ffff8801d007f9a0
---[ end trace 574e41d97d242295 ]---
Kernel panic - not syncing: Fatal exception
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.

[syzbot]

syzkaller has found reproducer for the following crash on
61ad64080e039dce99a7f8d89b729bbea995e2f7
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.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+114b15...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed.

audit: type=1400 audit(1515567598.363:9): avc: denied { prog_run } for
pid=3503 comm="syzkaller938388"
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=bpf
permissive=1

------------[ cut here ]------------
kernel BUG at net/l2tp/l2tp_ppp.c:176!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:

CPU: 1 PID: 3503 Comm: syzkaller938388 Not tainted 4.15.0-rc7+ #181

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:pppol2tp_sock_to_session net/l2tp/l2tp_ppp.c:176 [inline]

RIP: 0010:pppol2tp_sendmsg+0x512/0x670 net/l2tp/l2tp_ppp.c:304
RSP: 0018:ffff8801d4887438 EFLAGS: 00010293
RAX: ffff8801bfef2180 RBX: ffff8801bff88440 RCX: ffffffff84ffbca2
RDX: 0000000000000000 RSI: ffff8801d4887598 RDI: ffff8801bff88820
RBP: ffff8801d48874a8 R08: 0000000000000000 R09: 1ffff1003a910e17
R10: 0000000000000003 R11: 0000000000000001 R12: ffff8801bfff9bc0
R13: 0000000000000000 R14: 0000000000008000 R15: 0000000000000000
FS: 0000000001194880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000020ea0000 CR3: 00000001bfecf001 CR4: 00000000001606e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
sock_sendmsg_nosec net/socket.c:628 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:638

kernel_sendmsg+0x47/0x60 net/socket.c:646
sock_no_sendpage+0x1cc/0x280 net/core/sock.c:2581
kernel_sendpage+0xbf/0xe0 net/socket.c:3349
kcm_write_msgs+0x404/0x1b80 net/kcm/kcmsock.c:646
kcm_sendmsg+0x148d/0x22d0 net/kcm/kcmsock.c:1035

sock_sendmsg_nosec net/socket.c:628 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:638

___sys_sendmsg+0x767/0x8b0 net/socket.c:2018
__sys_sendmsg+0xe5/0x210 net/socket.c:2052
SYSC_sendmsg net/socket.c:2063 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2059
entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x440159
RSP: 002b:00007ffe74df8288 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000440159
RDX: 0000000000000000 RSI: 00000000201fcfc8 RDI: 0000000000000005
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000401ac0
R13: 0000000000401b50 R14: 0000000000000000 R15: 0000000000000000
Code: c5 61 70 fc 48 8b 7d d0 e8 7c c2 5b fd 84 c0 74 0d e8 b3 61 70 fc 48
89 df e8 3b 49 2f ff 41 bd f7 ff ff ff eb 86 e8 9e 61 70 fc <0f> 0b 41 bd
95 ff ff ff e9 74 ff ff ff e8 ec 32 a8 fc e9 77 fb

RIP: pppol2tp_sock_to_session net/l2tp/l2tp_ppp.c:176 [inline] RSP:

ffff8801d4887438
RIP: pppol2tp_sendmsg+0x512/0x670 net/l2tp/l2tp_ppp.c:304 RSP:
ffff8801d4887438
---[ end trace 801e405e4a8b3e54 ]---