WARNING in skb_warn_bad_offload

[syzbot]

Hello,

syzkaller hit the following crash on
720bbe532b7c8f5613b48dea627fc58ed9ace707
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


------------[ cut here ]------------
WARNING: CPU: 0 PID: 2986 at net/core/dev.c:2585
skb_warn_bad_offload+0x2a9/0x380 net/core/dev.c:2580
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 2986 Comm: syzkaller546001 Not tainted 4.13.0-mm1+ #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:52
panic+0x1e4/0x417 kernel/panic.c:181
__warn+0x1c4/0x1d9 kernel/panic.c:542
report_bug+0x211/0x2d0 lib/bug.c:183
fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178
do_trap_no_signal arch/x86/kernel/traps.c:212 [inline]
do_trap+0x260/0x390 arch/x86/kernel/traps.c:261
do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311
invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
RIP: 0010:skb_warn_bad_offload+0x2a9/0x380 net/core/dev.c:2580
RSP: 0018:ffff8801ce73f0a0 EFLAGS: 00010282
RAX: 000000000000006f RBX: ffff8801cd84cde0 RCX: 0000000000000000
RDX: 000000000000006f RSI: 1ffff10039ce7dd4 RDI: ffffed0039ce7e08
RBP: ffff8801ce73f0f8 R08: ffff8801ce73e790 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ce7802c0
R13: 0000000000000000 R14: ffff8801ce7802c0 R15: 0000000000002111
__skb_gso_segment+0x607/0x7f0 net/core/dev.c:2791
skb_gso_segment include/linux/netdevice.h:3951 [inline]
validate_xmit_skb+0x4ba/0xb20 net/core/dev.c:3041
validate_xmit_skb_list+0xb7/0x120 net/core/dev.c:3092
sch_direct_xmit+0x3b6/0x6d0 net/sched/sch_generic.c:181
__dev_xmit_skb net/core/dev.c:3173 [inline]
__dev_queue_xmit+0x15fe/0x1e40 net/core/dev.c:3440
dev_queue_xmit+0x17/0x20 net/core/dev.c:3505
packet_snd net/packet/af_packet.c:2950 [inline]
packet_sendmsg+0x3bbf/0x6030 net/packet/af_packet.c:2975
sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643
___sys_sendmsg+0x75b/0x8a0 net/socket.c:2049
__sys_sendmsg+0xe5/0x210 net/socket.c:2083
SYSC_sendmsg net/socket.c:2094 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2090
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x445489
RSP: 002b:00000000007efe68 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000445489
RDX: 0000000000004010 RSI: 00000000207fcfc8 RDI: 0000000000000004
RBP: 0000000000000082 R08: 000000000000cdf3 R09: 000000000000cdf3
R10: 0000000000000004 R11: 0000000000000217 R12: 0000000000402ae0
R13: 0000000000402b70 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Dmitry Vyukov]

On Wed, Nov 1, 2017 at 9:48 PM, syzbot
<bot+abb66e15eb1b298dfe...@syzkaller.appspotmail.com>
wrote:

> Hello,
>
> syzkaller hit the following crash on
> 720bbe532b7c8f5613b48dea627fc58ed9ace707
> 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

This also happens on more recent commits, including linux-next
36ef71cae353f88fd6e095e2aaa3e5953af1685d (Oct 20):

syz0: caps=(0x00000400000058c1, 0x0000000000000000) len=4203
data_len=2810 gso_size=8465 gso_type=3 ip_summed=0
------------[ cut here ]------------
WARNING: CPU: 0 PID: 3473 at net/core/dev.c:2618
skb_warn_bad_offload.cold.139+0x224/0x261 net/core/dev.c:2613

Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3473 Comm: a.out Not tainted 4.14.0-rc5-next-20171018 #15
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011

Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]

dump_stack+0x1a8/0x272 lib/dump_stack.c:52
panic+0x21e/0x4b7 kernel/panic.c:183
__warn.cold.6+0x182/0x187 kernel/panic.c:546
report_bug+0x232/0x330 lib/bug.c:183
fixup_bug+0x3f/0x90 arch/x86/kernel/traps.c:177
do_trap_no_signal arch/x86/kernel/traps.c:211 [inline]
do_trap+0x132/0x280 arch/x86/kernel/traps.c:260
do_error_trap+0x11f/0x390 arch/x86/kernel/traps.c:297
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:310
invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
RIP: 0010:skb_warn_bad_offload.cold.139+0x224/0x261 net/core/dev.c:2613
RSP: 0018:ffff880064797038 EFLAGS: 00010286
RAX: 000000000000006f RBX: ffff88006365efe8 RCX: 0000000000000000
RDX: 000000000000006f RSI: ffffffff815c88c1 RDI: ffffed000c8f2dfd
RBP: ffff880064797090 R08: ffff8800686f86c0 R09: 0000000000000002
R10: ffff8800686f86c0 R11: 0000000000000000 R12: ffff8800538b1680
R13: 0000000000000000 R14: ffff8800538b1680 R15: 0000000000002111
__skb_gso_segment+0x69e/0x860 net/core/dev.c:2824
skb_gso_segment include/linux/netdevice.h:3971 [inline]
validate_xmit_skb+0x29f/0xca0 net/core/dev.c:3074
validate_xmit_skb_list+0xb7/0x120 net/core/dev.c:3125
sch_direct_xmit+0x5b5/0x710 net/sched/sch_generic.c:181
__dev_xmit_skb net/core/dev.c:3206 [inline]
__dev_queue_xmit+0x1e41/0x2350 net/core/dev.c:3473
dev_queue_xmit+0x17/0x20 net/core/dev.c:3538
packet_snd net/packet/af_packet.c:2956 [inline]
packet_sendmsg+0x487a/0x64b0 net/packet/af_packet.c:2981
sock_sendmsg_nosec net/socket.c:632 [inline]
sock_sendmsg+0xd2/0x120 net/socket.c:642
___sys_sendmsg+0x7cc/0x900 net/socket.c:2048
__sys_sendmsg+0xe6/0x220 net/socket.c:2082
SYSC_sendmsg net/socket.c:2093 [inline]
SyS_sendmsg+0x36/0x60 net/socket.c:2089
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x44bab9
RSP: 002b:00000000007eff18 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000020001046 RCX: 000000000044bab9

RDX: 0000000000004010 RSI: 00000000207fcfc8 RDI: 0000000000000004

RBP: 0000000000000086 R08: 850b2da14d2a3706 R09: 0000000000000000
R10: 1b91126b7f398aaa R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000407950 R14: 00000000004079e0 R15: 0000000000000000

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[Eric Biggers]

Apparently fixed by commit 8d74e9f88d65a, so telling syzbot:

#syz fix: net: avoid skb_warn_bad_offload on IS_ERR

- Eric