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BUG: KASAN: slab-out-of-bounds in erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
Read of size 2 at addr ffff8801d6e1800b by task syz-executor0/5964

CPU: 0 PID: 5964 Comm: syz-executor0 Not tainted 4.15.0-rc9+ #276
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_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
 erspan_xmit+0x3b8/0x13b0 net/ipv4/ip_gre.c:740
 __netdev_start_xmit include/linux/netdevice.h:4042 [inline]
 netdev_start_xmit include/linux/netdevice.h:4051 [inline]
 packet_direct_xmit+0x315/0x6b0 net/packet/af_packet.c:266
 packet_snd net/packet/af_packet.c:2943 [inline]
 packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2968
 sock_sendmsg_nosec net/socket.c:638 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:648
 SYSC_sendto+0x361/0x5c0 net/socket.c:1729
 SyS_sendto+0x40/0x50 net/socket.c:1697
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452f19
RSP: 002b:00007fc06c459c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 0000000000000000 RSI: 0000000020015f41 RDI: 0000000000000013
RBP: 0000000000000077 R08: 0000000020015fec R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006efbc8
R13: 00000000ffffffff R14: 00007fc06c45a6d4 R15: 0000000000000000

Allocated by task 1:
 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]
 tty_register_device_attr+0x2b3/0x770 drivers/tty/tty_io.c:2942
 tty_register_device drivers/tty/tty_io.c:2890 [inline]
 tty_register_driver+0x423/0xab0 drivers/tty/tty_io.c:3161
 vty_init+0x36e/0x3a0 drivers/tty/vt/vt.c:3100
 tty_init+0x146/0x14a drivers/tty/tty_io.c:3319
 chr_dev_init+0x12c/0x13e drivers/char/mem.c:925
 do_one_initcall+0xad/0x357 init/main.c:832
 do_initcall_level init/main.c:898 [inline]
 do_initcalls init/main.c:906 [inline]
 do_basic_setup init/main.c:924 [inline]
 kernel_init_freeable+0x469/0x521 init/main.c:1072
 kernel_init+0x13/0x180 init/main.c:999
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801d6e18640
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1589 bytes to the left of
 2048-byte region [ffff8801d6e18640, ffff8801d6e18e40)
The buggy address belongs to the page:
page:ffffea00075b8600 count:1 mapcount:0 mapping:ffff8801d6e18640 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d6e18640 0000000000000000 0000000100000003
raw: ffffea00075b58a0 ffffea00075b7d20 ffff8801dac00c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d6e17f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d6e17f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d6e18000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                      ^
 ffff8801d6e18080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d6e18100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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