BUG: KASAN: use-after-free in skb_release_data+0x5cf/0x790 net/core/skbuff.c:567
Read of size 1 at addr ffff8800687f7d42 by task syz-executor0/3331

CPU: 2 PID: 3331 Comm: syz-executor0 Not tainted 4.13.0-rc5-next-20170815+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x24e/0x340 mm/kasan/report.c:409
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
 skb_release_data+0x5cf/0x790 net/core/skbuff.c:567
 skb_release_all+0x4a/0x60 net/core/skbuff.c:631
 __kfree_skb net/core/skbuff.c:645 [inline]
 kfree_skb+0x15d/0x4c0 net/core/skbuff.c:663
 ip_frag_queue net/ipv4/ip_fragment.c:474 [inline]
 ip_defrag+0xc69/0x4000 net/ipv4/ip_fragment.c:680
 ip_local_deliver+0x174/0x6d0 net/ipv4/ip_input.c:253
 dst_input include/net/dst.h:477 [inline]
 ip_rcv_finish+0x8db/0x19c0 net/ipv4/ip_input.c:397
 NF_HOOK include/linux/netfilter.h:248 [inline]
 ip_rcv+0xc3f/0x17d0 net/ipv4/ip_input.c:488
 __netif_receive_skb_core+0x19af/0x33d0 net/core/dev.c:4418
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4456
 netif_receive_skb_internal+0x10b/0x5e0 net/core/dev.c:4527
 netif_receive_skb+0xae/0x390 net/core/dev.c:4551
 tun_rx_batched.isra.43+0x5e7/0x860 drivers/net/tun.c:1221
 tun_get_user+0x11dd/0x2150 drivers/net/tun.c:1542
 tun_chr_write_iter+0xd8/0x190 drivers/net/tun.c:1568
 call_write_iter include/linux/fs.h:1742 [inline]
 new_sync_write fs/read_write.c:457 [inline]
 __vfs_write+0x684/0x970 fs/read_write.c:470
 vfs_write+0x189/0x510 fs/read_write.c:518
 SYSC_write fs/read_write.c:565 [inline]
 SyS_write+0xef/0x220 fs/read_write.c:557
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x40bab1
RSP: 002b:00007fe09e61cc00 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000000002a RCX: 000000000040bab1
RDX: 000000000000002a RSI: 0000000020a71fd0 RDI: 0000000000000003
RBP: 0000000000708000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00000000ffffffff
R13: 00000000000056b0 R14: 00000000006e7770 R15: 0000000001010200

The buggy address belongs to the page:
page:ffffea0001a1fdc0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x500000000000000()
raw: 0500000000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 0000000100000001 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8800687f7c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8800687f7c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8800687f7d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8800687f7d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8800687f7e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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