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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 ffff8801c1637b0b by task syz-executor3/20714

CPU: 0 PID: 20714 Comm: syz-executor3 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:00007f863380dc58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 000000000000004d RSI: 0000000020003000 RDI: 0000000000000013
RBP: 000000000000059c R08: 0000000020008000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7740
R13: 00000000ffffffff R14: 00007f863380e6d4 R15: 0000000000000000

Allocated by task 19087:
 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_flags+0xcb/0x580 fs/namei.c:138
 user_path_at_empty+0x2d/0x50 fs/namei.c:2590
 user_path_at include/linux/namei.h:57 [inline]
 SYSC_chdir fs/open.c:440 [inline]
 SyS_chdir+0xb0/0x200 fs/open.c:434
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 19087:
 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
 filename_lookup+0x315/0x500 fs/namei.c:2345
 user_path_at_empty+0x40/0x50 fs/namei.c:2590
 user_path_at include/linux/namei.h:57 [inline]
 SYSC_chdir fs/open.c:440 [inline]
 SyS_chdir+0xb0/0x200 fs/open.c:434
 entry_SYSCALL_64_fastpath+0x29/0xa0

The buggy address belongs to the object at ffff8801c1636a00
 which belongs to the cache names_cache of size 4096
The buggy address is located 267 bytes to the right of
 4096-byte region [ffff8801c1636a00, ffff8801c1637a00)
The buggy address belongs to the page:
page:ffffea0007058d80 count:1 mapcount:0 mapping:ffff8801c1636a00 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801c1636a00 0000000000000000 0000000100000001
raw: ffffea00070d8520 ffffea00073dc320 ffff8801dae2c600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c1637a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c1637a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c1637b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                      ^
 ffff8801c1637b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c1637c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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