syzbot

device lo entered promiscuous mode
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BUG: KASAN: use-after-free in neigh_flush_dev+0x817/0x840 net/core/neighbour.c:244
Read of size 8 at addr ffff8801d8403680 by task syz-executor4/10275

CPU: 1 PID: 10275 Comm: syz-executor4 Not tainted 4.15.0-rc4+ #164
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
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 neigh_flush_dev+0x817/0x840 net/core/neighbour.c:244
 neigh_ifdown+0x48/0x250 net/core/neighbour.c:293
 addrconf_ifdown+0x143/0x14d0 net/ipv6/addrconf.c:3590
 addrconf_notify+0x98e/0x21c0 net/ipv6/addrconf.c:3514
 notifier_call_chain+0x136/0x2c0 kernel/notifier.c:93
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
 call_netdevice_notifiers_info+0x32/0x60 net/core/dev.c:1696
 call_netdevice_notifiers net/core/dev.c:1714 [inline]
 __dev_notify_flags+0x15d/0x430 net/core/dev.c:6892
 dev_change_flags+0xf5/0x140 net/core/dev.c:6928
 devinet_ioctl+0x125b/0x19c0 net/ipv4/devinet.c:1083
 inet_ioctl+0x117/0x1c0 net/ipv4/af_inet.c:903
 sock_do_ioctl+0x65/0xb0 net/socket.c:956
 sock_ioctl+0x2c2/0x440 net/socket.c:1053
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452ac9
RSP: 002b:00007fd629eaac58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ac9
RDX: 000000002003b000 RSI: 0000000000008914 RDI: 0000000000000016
RBP: 000000000000055d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f5158
R13: 00000000ffffffff R14: 00007fd629eab6d4 R15: 0000000000000000

Allocated by task 7650:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 __do_kmalloc mm/slab.c:3708 [inline]
 __kmalloc+0x162/0x760 mm/slab.c:3717
 kmalloc include/linux/slab.h:504 [inline]
 kzalloc include/linux/slab.h:688 [inline]
 neigh_alloc net/core/neighbour.c:322 [inline]
 __neigh_create+0x296/0x1d90 net/core/neighbour.c:493
 ip6_finish_output2+0x91b/0x2310 net/ipv6/ip6_output.c:117
 ip6_finish_output+0x2f9/0x920 net/ipv6/ip6_output.c:146
 NF_HOOK_COND include/linux/netfilter.h:239 [inline]
 ip6_output+0x1eb/0x840 net/ipv6/ip6_output.c:163
 dst_output include/net/dst.h:443 [inline]
 NF_HOOK.constprop.36+0xff/0x630 include/linux/netfilter.h:250
 mld_sendpack+0x6a9/0xcc0 net/ipv6/mcast.c:1660
 mld_send_cr net/ipv6/mcast.c:1956 [inline]
 mld_ifc_timer_expire+0x3d9/0x770 net/ipv6/mcast.c:2453
 call_timer_fn+0x228/0x820 kernel/time/timer.c:1320
 expire_timers kernel/time/timer.c:1357 [inline]
 __run_timers+0x7ee/0xb70 kernel/time/timer.c:1660
 run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

Freed by task 3004:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3488 [inline]
 kfree+0xd6/0x260 mm/slab.c:3803
 syslog_print kernel/printk/printk.c:1343 [inline]
 do_syslog+0x8b5/0xb80 kernel/printk/printk.c:1455
 kmsg_read+0x74/0xa0 fs/proc/kmsg.c:40
 proc_reg_read+0xef/0x170 fs/proc/inode.c:217
 __vfs_read+0xef/0xa00 fs/read_write.c:411
 vfs_read+0x11e/0x350 fs/read_write.c:447
 SYSC_read fs/read_write.c:573 [inline]
 SyS_read+0xef/0x220 fs/read_write.c:566
 entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801d8403680
 which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 0 bytes inside of
 1024-byte region [ffff8801d8403680, ffff8801d8403a80)
The buggy address belongs to the page:
page:00000000c916a8bc count:1 mapcount:0 mapping:00000000bb4b6d81 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d8402000 0000000000000000 0000000100000007
raw: ffffea00073a8a20 ffffea0006f3de20 ffff8801db000ac0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d8403580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d8403600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d8403680: fb fb fb fb 00 00 00 00 00 00 00 00 00 00 00 00
                   ^
 ffff8801d8403700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801d8403780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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