KASAN: use-after-free Read in ip_tunnel_lookup

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 01364dad Linux 4.14.174
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10ce9c97e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=664dd71881ab2b2d
dashboard link: https://syzkaller.appspot.com/bug?extid=c0d9481d7996f0515957
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c0d948...@syzkaller.appspotmail.com

batman_adv: batadv0: Interface deactivated: batadv_slave_0
==================================================================
BUG: KASAN: use-after-free in ip_tunnel_lookup+0x9d3/0xb70 net/ipv4/ip_tunnel.c:142
Read of size 4 at addr ffff888059c57384 by task ksoftirqd/1/17

CPU: 1 PID: 17 Comm: ksoftirqd/1 Not tainted 4.14.174-syzkaller #0
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+0x13e/0x194 lib/dump_stack.c:58
print_address_description.cold+0x7c/0x1e2 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2ae mm/kasan/report.c:393
ip_tunnel_lookup+0x9d3/0xb70 net/ipv4/ip_tunnel.c:142
vti4_err+0x28f/0x960 net/ipv4/ip_vti.c:334
tunnel4_err+0x81/0x160 net/ipv4/tunnel4.c:157
icmp_socket_deliver+0x1ba/0x330 net/ipv4/icmp.c:773
icmp_unreach+0x2de/0x9d0 net/ipv4/icmp.c:890
icmp_rcv+0x719/0x1300 net/ipv4/icmp.c:1071
ip_local_deliver_finish+0x245/0xaa0 net/ipv4/ip_input.c:216
NF_HOOK include/linux/netfilter.h:250 [inline]
NF_HOOK include/linux/netfilter.h:244 [inline]
ip_local_deliver+0x1a6/0x450 net/ipv4/ip_input.c:257
dst_input include/net/dst.h:468 [inline]
ip_rcv_finish+0x79b/0x1a10 net/ipv4/ip_input.c:396
NF_HOOK include/linux/netfilter.h:250 [inline]
NF_HOOK include/linux/netfilter.h:244 [inline]
ip_rcv+0x9d8/0xfec net/ipv4/ip_input.c:493
__netif_receive_skb_core+0x1e50/0x2c00 net/core/dev.c:4477
__netif_receive_skb+0x27/0x1a0 net/core/dev.c:4515
process_backlog+0x214/0x750 net/core/dev.c:5197
napi_poll net/core/dev.c:5598 [inline]
net_rx_action+0x456/0xe90 net/core/dev.c:5664
__do_softirq+0x254/0x9bf kernel/softirq.c:288
run_ksoftirqd kernel/softirq.c:670 [inline]
run_ksoftirqd+0x87/0x1a0 kernel/softirq.c:662
smpboot_thread_fn+0x5c1/0x920 kernel/smpboot.c:164
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 7394:
save_stack+0x32/0xa0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc mm/kasan/kasan.c:551 [inline]
kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:529
__do_kmalloc_node mm/slab.c:3682 [inline]
__kmalloc_node+0x4c/0x70 mm/slab.c:3689
kmalloc_node include/linux/slab.h:530 [inline]
kvmalloc_node+0x46/0xd0 mm/util.c:397
kvmalloc include/linux/mm.h:531 [inline]
kvzalloc include/linux/mm.h:539 [inline]
alloc_netdev_mqs+0x76/0xb70 net/core/dev.c:8097
__ip_tunnel_create+0x16a/0x440 net/ipv4/ip_tunnel.c:269
ip_tunnel_init_net+0x272/0x520 net/ipv4/ip_tunnel.c:1039
vti_init_net+0x2a/0x2f0 net/ipv4/ip_vti.c:497
ops_init+0xa5/0x3c0 net/core/net_namespace.c:118
setup_net+0x22f/0x500 net/core/net_namespace.c:295
copy_net_ns+0x19b/0x440 net/core/net_namespace.c:419
create_new_namespaces+0x375/0x730 kernel/nsproxy.c:107
unshare_nsproxy_namespaces+0xa5/0x1e0 kernel/nsproxy.c:206
SYSC_unshare kernel/fork.c:2391 [inline]
SyS_unshare+0x2ea/0x740 kernel/fork.c:2341
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 2216:
save_stack+0x32/0xa0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcb/0x260 mm/slab.c:3815
kvfree+0x45/0x50 mm/util.c:416
device_release+0x15f/0x1a0 drivers/base/core.c:833
kobject_cleanup lib/kobject.c:646 [inline]
kobject_release lib/kobject.c:675 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put+0x13e/0x1f0 lib/kobject.c:692
netdev_run_todo+0x4a9/0x710 net/core/dev.c:7954
ip_tunnel_delete_net+0x260/0x300 net/ipv4/ip_tunnel.c:1086
ops_exit_list.isra.0+0x9d/0x140 net/core/net_namespace.c:142
cleanup_net+0x3bb/0x820 net/core/net_namespace.c:484
process_one_work+0x813/0x1540 kernel/workqueue.c:2116
worker_thread+0x5d1/0x1070 kernel/workqueue.c:2250
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

The buggy address belongs to the object at ffff888059c56840
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 2884 bytes inside of
4096-byte region [ffff888059c56840, ffff888059c57840)
The buggy address belongs to the page:
page:ffffea0001671580 count:1 mapcount:0 mapping:ffff888059c56840 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff888059c56840 0000000000000000 0000000100000001
raw: ffffea0001671420 ffffea00016719a0 ffff88812fe56dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888059c57280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888059c57300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888059c57380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888059c57400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888059c57480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.