protocol 0000 is buggy, dev sit0
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BUG: KASAN: use-after-free in atomic_sub_return include/asm-generic/atomic-instrumented.h:258 [inline]
BUG: KASAN: use-after-free in skb_release_data+0x19b/0x860 net/core/skbuff.c:559
Write of size 4 at addr ffff8801afd36620 by task syz-executor4/19952

CPU: 0 PID: 19952 Comm: syz-executor4 Not tainted 4.17.0-rc4+ #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 kasan_check_write+0x14/0x20 mm/kasan/kasan.c:278
 atomic_sub_return include/asm-generic/atomic-instrumented.h:258 [inline]
 skb_release_data+0x19b/0x860 net/core/skbuff.c:559
 skb_release_all+0x4a/0x60 net/core/skbuff.c:627
 __kfree_skb net/core/skbuff.c:641 [inline]
 kfree_skb+0x195/0x560 net/core/skbuff.c:659
 sit_tunnel_xmit+0x16b/0x30b0 net/ipv6/sit.c:1044
 __netdev_start_xmit include/linux/netdevice.h:4099 [inline]
 netdev_start_xmit include/linux/netdevice.h:4108 [inline]
 xmit_one net/core/dev.c:3052 [inline]
 dev_hard_start_xmit+0x264/0xc10 net/core/dev.c:3068
 __dev_queue_xmit+0x292f/0x3910 net/core/dev.c:3587
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3620
 packet_snd net/packet/af_packet.c:2919 [inline]
 packet_sendmsg+0x40bc/0x6020 net/packet/af_packet.c:2944
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:639
 ___sys_sendmsg+0x805/0x940 net/socket.c:2117
 __sys_sendmsg+0x115/0x270 net/socket.c:2155
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455a09
RSP: 002b:00007f621b8f6c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f621b8f76d4 RCX: 0000000000455a09
RDX: 0000000000000000 RSI: 0000000020001c00 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000057f R14: 00000000006fc488 R15: 0000000000000000

Allocated by task 19952:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 __do_kmalloc_node mm/slab.c:3682 [inline]
 __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696
 __kmalloc_reserve.isra.39+0x3a/0xe0 net/core/skbuff.c:137
 __alloc_skb+0x14d/0x780 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:989 [inline]
 alloc_skb_with_frags+0x137/0x760 net/core/skbuff.c:5266
 sock_alloc_send_pskb+0x87a/0xae0 net/core/sock.c:2095
 packet_alloc_skb net/packet/af_packet.c:2778 [inline]
 packet_snd net/packet/af_packet.c:2869 [inline]
 packet_sendmsg+0x1b87/0x6020 net/packet/af_packet.c:2944
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:639
 ___sys_sendmsg+0x805/0x940 net/socket.c:2117
 __sys_sendmsg+0x115/0x270 net/socket.c:2155
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 19952:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xd9/0x260 mm/slab.c:3813
 skb_free_head+0x99/0xc0 net/core/skbuff.c:550
 skb_release_data+0x690/0x860 net/core/skbuff.c:570
 skb_release_all+0x4a/0x60 net/core/skbuff.c:627
 __kfree_skb net/core/skbuff.c:641 [inline]
 consume_skb+0x18b/0x550 net/core/skbuff.c:701
 packet_rcv+0x16a/0x1810 net/packet/af_packet.c:2137
 dev_queue_xmit_nit+0x90c/0xc50 net/core/dev.c:2019
 xmit_one net/core/dev.c:3048 [inline]
 dev_hard_start_xmit+0x16b/0xc10 net/core/dev.c:3068
 __dev_queue_xmit+0x292f/0x3910 net/core/dev.c:3587
 dev_queue_xmit+0x17/0x20 net/core/dev.c:3620
 packet_snd net/packet/af_packet.c:2919 [inline]
 packet_sendmsg+0x40bc/0x6020 net/packet/af_packet.c:2944
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:639
 ___sys_sendmsg+0x805/0x940 net/socket.c:2117
 __sys_sendmsg+0x115/0x270 net/socket.c:2155
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801afd36540
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 224 bytes inside of
 512-byte region [ffff8801afd36540, ffff8801afd36740)
The buggy address belongs to the page:
page:ffffea0006bf4d80 count:1 mapcount:0 mapping:ffff8801afd36040 index:0xffff8801afd362c0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801afd36040 ffff8801afd362c0 0000000100000004
raw: ffffea0006d57ce0 ffffea0006d2c7a0 ffff8801da800940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801afd36500: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8801afd36580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801afd36600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8801afd36680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801afd36700: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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