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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 ffff8801d460090b by task syz-executor0/26340

CPU: 0 PID: 26340 Comm: syz-executor0 Not tainted 4.15.0-rc9+ #206
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:00007f40f4bd3c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 0000000000000081 RSI: 0000000020001000 RDI: 0000000000000013
RBP: 000000000000059c R08: 0000000020008000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7740
R13: 00000000ffffffff R14: 00007f40f4bd46d4 R15: 0000000000000000

Allocated by task 573:
 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_node mm/slab.c:3672 [inline]
 __kmalloc_node+0x47/0x70 mm/slab.c:3679
 kmalloc_node include/linux/slab.h:541 [inline]
 kvmalloc_node+0x99/0xd0 mm/util.c:397
 kvmalloc include/linux/mm.h:541 [inline]
 kvzalloc include/linux/mm.h:549 [inline]
 alloc_netdev_mqs+0x16d/0xfb0 net/core/dev.c:8263
 ip6mr_reg_vif net/ipv6/ip6mr.c:748 [inline]
 mif6_add net/ipv6/ip6mr.c:949 [inline]
 ip6_mroute_setsockopt+0x8b7/0x35b0 net/ipv6/ip6mr.c:1708
 do_ipv6_setsockopt.isra.9+0x2f0/0x39a0 net/ipv6/ipv6_sockglue.c:163
 ipv6_setsockopt+0xd7/0x150 net/ipv6/ipv6_sockglue.c:922
 rawv6_setsockopt+0x4a/0xf0 net/ipv6/raw.c:1060
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
 SYSC_setsockopt net/socket.c:1823 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1802
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 28567:
 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 ffff8801d4600c80
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 885 bytes to the left of
 4096-byte region [ffff8801d4600c80, ffff8801d4601c80)
The buggy address belongs to the page:
page:ffffea0007518000 count:1 mapcount:0 mapping:ffff8801d4600c80 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d4600c80 0000000000000000 0000000100000001
raw: ffffea00073fb5a0 ffffea00071c1c20 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d4600800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d4600880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d4600900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                      ^
 ffff8801d4600980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d4600a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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