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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 ffff8801c17d258b by task syz-executor6/18670

CPU: 0 PID: 18670 Comm: syz-executor6 Not tainted 4.15.0-rc8+ #204
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:00007f6e0d9e8c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f6e0d9e9700 RCX: 0000000000452f19
RDX: 0000000000000000 RSI: 0000000020003fd9 RDI: 0000000000000013
RBP: 0000000000000000 R08: 0000000020008000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a2f7cf R14: 00007f6e0d9e99c0 R15: 0000000000000000

Allocated by task 15645:
 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
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
 getname_kernel+0x54/0x340 fs/namei.c:218
 call_usermodehelper_exec_async+0x449/0x8f0 kernel/umh.c:100
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

Freed by task 15645:
 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]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
 putname+0xee/0x130 fs/namei.c:258
 do_execveat_common.isra.30+0x1a38/0x23c0 fs/exec.c:1814
 do_execve+0x31/0x40 fs/exec.c:1847
 call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

The buggy address belongs to the object at ffff8801c17d2780
 which belongs to the cache names_cache of size 4096
The buggy address is located 501 bytes to the left of
 4096-byte region [ffff8801c17d2780, ffff8801c17d3780)
The buggy address belongs to the page:
page:ffffea000705f480 count:1 mapcount:0 mapping:ffff8801c17d2780 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c17d2780 0000000000000000 0000000100000001
raw: ffffea0007422aa0 ffffea0006ed2da0 ffff8801dae2c600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c17d2480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c17d2500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c17d2580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                      ^
 ffff8801c17d2600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c17d2680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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