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BUG: KASAN: slab-out-of-bounds in erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
Read of size 2 at addr ffff8801bcedeccb by task syz-executor2/31647

CPU: 1 PID: 31647 Comm: syz-executor2 Not tainted 4.15.0-rc8+ #205
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_load_n_noabort+0xf/0x20 mm/kasan/report.c:440
 erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
 __netdev_start_xmit include/linux/netdevice.h:4055 [inline]
 netdev_start_xmit include/linux/netdevice.h:4064 [inline]
 packet_direct_xmit+0x3ad/0x790 net/packet/af_packet.c:267
 packet_snd net/packet/af_packet.c:2944 [inline]
 packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2969
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 SYSC_sendto+0x361/0x5c0 net/socket.c:1721
 SyS_sendto+0x40/0x50 net/socket.c:1689
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452f19
RSP: 002b:00007f107c41cc58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bf58 RCX: 0000000000452f19
RDX: 000000000000033e RSI: 0000000020003fd9 RDI: 0000000000000013
RBP: 00000000000005ce R08: 0000000020018000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7bf0
R13: 00000000ffffffff R14: 00007f107c41d6d4 R15: 000000000000000b

Allocated by task 10862:
 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_track_caller+0x15e/0x760 mm/slab.c:3723
 kmemdup+0x24/0x50 mm/util.c:118
 kmemdup include/linux/string.h:417 [inline]
 __addrconf_sysctl_register+0xae/0x400 net/ipv6/addrconf.c:6385
 addrconf_sysctl_register+0x116/0x1b0 net/ipv6/addrconf.c:6450
 ipv6_add_dev+0xa3d/0x1310 net/ipv6/addrconf.c:458
 addrconf_notify+0x86e/0x2310 net/ipv6/addrconf.c:3380
 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+0x32/0x70 net/core/dev.c:1708
 call_netdevice_notifiers net/core/dev.c:1726 [inline]
 register_netdevice+0xd40/0x1020 net/core/dev.c:7869
 register_netdev+0x1a/0x30 net/core/dev.c:7954
 br_add_bridge+0x97/0xd0 net/bridge/br_if.c:394
 old_deviceless net/bridge/br_ioctl.c:349 [inline]
 br_ioctl_deviceless_stub+0x8fe/0xa00 net/bridge/br_ioctl.c:363
 sock_ioctl+0x383/0x440 net/socket.c:1022
 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+0x29/0xa0

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801bcedee40
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 373 bytes to the left of
 4096-byte region [ffff8801bcedee40, ffff8801bcedfe40)
The buggy address belongs to the page:
page:ffffea0006f3b780 count:1 mapcount:0 mapping:ffff8801bcedee40 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801bcedee40 0000000000000000 0000000100000001
raw: ffffea0006f3b720 ffffea0006f83c20 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bcedeb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bcedec00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801bcedec80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff8801bceded00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bceded80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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