kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 3 PID: 4307 Comm: syz-executor0 Not tainted 4.13.0-rc5-next-20170816+ #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88003a7d8240 task.stack: ffff88002f800000
RIP: 0010:__read_once_size include/linux/compiler.h:276 [inline]
RIP: 0010:compound_head include/linux/page-flags.h:146 [inline]
RIP: 0010:put_page include/linux/mm.h:811 [inline]
RIP: 0010:__skb_frag_unref include/linux/skbuff.h:2743 [inline]
RIP: 0010:skb_release_data+0x26c/0x790 net/core/skbuff.c:568
RSP: 0018:ffff88002f806f20 EFLAGS: 00010202
RAX: 0823216ad559c097 RBX: dffffc0000000000 RCX: ffffc90000e41000
RDX: 000000000000014a RSI: ffffffff83e00427 RDI: 41190b56aace04bb
RBP: ffff88002f807040 R08: 0000000000000001 R09: 0000000000000000
R10: ffff88002f8076b0 R11: ffffffff85b34c40 R12: ffff880030af97b0
R13: ffffed0005f00dfb R14: 1ffff10005f00df3 R15: 41190b56aace049b
FS:  00007fa9ce866700(0000) GS:ffff88006df00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa9ef5e7000 CR3: 000000003a76b000 CR4: 00000000000006e0
Call Trace:
 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
 __netif_receive_skb_core+0x10f8/0x33d0 net/core/dev.c:4425
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4456
 netif_receive_skb_internal+0x10b/0x5e0 net/core/dev.c:4527
sctp: [Deprecated]: syz-executor1 (pid 4302) Use of int in maxseg socket option.
Use struct sctp_assoc_value instead
 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:00007fa9ce865c00 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000038 RCX: 000000000040bab1
RDX: 0000000000000038 RSI: 0000000020004000 RDI: 0000000000000015
RBP: 0000000000708000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00000000ffffffff
R13: 00000000000057b0 R14: 00000000006e7870 R15: 0000000000400008
Code: c6 e8 c9 68 8d fd 4c 89 e0 48 c1 e8 03 80 3c 18 00 0f 85 93 04 00 00 4d 8b 3c 24 41 c6 45 00 00 49 8d 7f 20 48 89 f8 48 c1 e8 03 <80> 3c 18 00 0f 85 6b 04 00 00 41 80 7d 00 00 49 8b 47 20 0f 85 
RIP: __read_once_size include/linux/compiler.h:276 [inline] RSP: ffff88002f806f20
RIP: compound_head include/linux/page-flags.h:146 [inline] RSP: ffff88002f806f20
RIP: put_page include/linux/mm.h:811 [inline] RSP: ffff88002f806f20
RIP: __skb_frag_unref include/linux/skbuff.h:2743 [inline] RSP: ffff88002f806f20
RIP: skb_release_data+0x26c/0x790 net/core/skbuff.c:568 RSP: ffff88002f806f20
---[ end trace f3d396965d4b0d42 ]---