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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 ffff8801c35d254b by task syz-executor0/27062

CPU: 0 PID: 27062 Comm: syz-executor0 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:00007f5563fb9c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 0000000000000000 RSI: 0000000020018000 RDI: 0000000000000013
RBP: 00000000000003d6 R08: 0000000020009fe4 R09: 000000000000001c
R10: 0000010000000000 R11: 0000000000000212 R12: 00000000006f4cb0
R13: 00000000ffffffff R14: 00007f5563fba6d4 R15: 0000000000000000

Allocated by task 30316:
 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
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
 kmalloc include/linux/slab.h:499 [inline]
 kzalloc include/linux/slab.h:688 [inline]
 vlan_group_prealloc_vid net/8021q/vlan.c:70 [inline]
 register_vlan_dev+0x368/0x650 net/8021q/vlan.c:163
 register_vlan_device net/8021q/vlan.c:268 [inline]
 vlan_ioctl_handler+0xbfb/0x1186 net/8021q/vlan.c:588
 sock_ioctl+0x285/0x440 net/socket.c:1033
 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 25862:
 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
 kvfree+0x36/0x60 mm/util.c:416
 seq_release fs/seq_file.c:365 [inline]
 single_release+0x78/0xb0 fs/seq_file.c:602
 close_pdeo+0x14f/0x530 fs/proc/inode.c:165
 proc_reg_release+0x12b/0x170 fs/proc/inode.c:376
 __fput+0x327/0x7e0 fs/file_table.c:210
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x199/0x270 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x296/0x310 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
 entry_SYSCALL_64_fastpath+0x9e/0xa0

The buggy address belongs to the object at ffff8801c35d2d00
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 1973 bytes to the left of
 4096-byte region [ffff8801c35d2d00, ffff8801c35d3d00)
The buggy address belongs to the page:
page:ffffea00070d7480 count:1 mapcount:0 mapping:ffff8801c35d2d00 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c35d2d00 0000000000000000 0000000100000001
raw: ffffea00071ab620 ffffea00070a0ea0 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c35d2400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c35d2480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c35d2500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff8801c35d2580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c35d2600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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