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BUG: KASAN: use-after-free in erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
Read of size 2 at addr ffff8801d4204dcb by task syz-executor3/21576

CPU: 0 PID: 21576 Comm: syz-executor3 Not tainted 4.15.0-rc8+ #203
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:4053 [inline]
 netdev_start_xmit include/linux/netdevice.h:4062 [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: 0033:0x452ef9
RSP: 002b:00007f10590c0c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ef9
RDX: 0000000000000097 RSI: 0000000020011f69 RDI: 0000000000000013
RBP: 0000000000000114 R08: 0000000020011fe4 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f0a80
R13: 00000000ffffffff R14: 00007f10590c16d4 R15: 0000000000000000

Allocated by task 20426:
 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_track_caller+0x47/0x70 mm/slab.c:3686
 __kmalloc_reserve.isra.39+0x41/0xd0 net/core/skbuff.c:137
 __alloc_skb+0x13b/0x780 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:983 [inline]
 alloc_skb_with_frags+0x10d/0x750 net/core/skbuff.c:5151
 sock_alloc_send_pskb+0x787/0x9b0 net/core/sock.c:2088
 unix_dgram_sendmsg+0x52d/0x1610 net/unix/af_unix.c:1682
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 ___sys_sendmsg+0x320/0x8b0 net/socket.c:2020
 __sys_sendmmsg+0x1ee/0x620 net/socket.c:2110
 SYSC_sendmmsg net/socket.c:2141 [inline]
 SyS_sendmmsg+0x35/0x60 net/socket.c:2136
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 20426:
 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
 skb_free_head+0x74/0xb0 net/core/skbuff.c:550
 skb_release_data+0x58c/0x790 net/core/skbuff.c:570
 skb_release_all+0x4a/0x60 net/core/skbuff.c:627
 __kfree_skb net/core/skbuff.c:641 [inline]
 kfree_skb+0x15d/0x4c0 net/core/skbuff.c:659
 unix_release_sock+0x5e3/0xc10 net/unix/af_unix.c:560
 unix_release+0x44/0x90 net/unix/af_unix.c:838
 sock_release+0x8d/0x1e0 net/socket.c:595
 sock_close+0x16/0x20 net/socket.c:1123
 __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
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x9bb/0x1ad0 kernel/exit.c:865
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73f/0x16c0 kernel/signal.c:2335
 do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 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 ffff8801d4204d00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 203 bytes inside of
 512-byte region [ffff8801d4204d00, ffff8801d4204f00)
The buggy address belongs to the page:
page:ffffea0007508100 count:1 mapcount:0 mapping:ffff8801d4204080 index:0xffff8801d4204800
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d4204080 ffff8801d4204800 0000000100000005
raw: ffffea000739ef20 ffffea000759dba0 ffff8801dac00940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d4204c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d4204d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d4204d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8801d4204e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d4204e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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