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BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:673 [inline]
BUG: KASAN: use-after-free in enqueue_timer kernel/time/timer.c:520 [inline]
BUG: KASAN: use-after-free in __mod_timer kernel/time/timer.c:1021 [inline]
BUG: KASAN: use-after-free in mod_timer_pending+0x11d5/0x14e0 kernel/time/timer.c:1045
Write of size 8 at addr ffff8801c73b3f08 by task syz-executor7/11906

CPU: 0 PID: 11906 Comm: syz-executor7 Not tainted 4.14.0-rc2-next-20170929+ #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 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+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435
 hlist_add_head include/linux/list.h:673 [inline]
 enqueue_timer kernel/time/timer.c:520 [inline]
 __mod_timer kernel/time/timer.c:1021 [inline]
 mod_timer_pending+0x11d5/0x14e0 kernel/time/timer.c:1045
 tcp_check_req+0x1193/0x1620 net/ipv4/tcp_minisocks.c:620
 tcp_v4_rcv+0x17ad/0x2f20 net/ipv4/tcp_ipv4.c:1674
 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257
 dst_input include/net/dst.h:464 [inline]
 ip_rcv_finish+0x8db/0x19c0 net/ipv4/ip_input.c:397
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_rcv+0xc3f/0x17d0 net/ipv4/ip_input.c:488
 __netif_receive_skb_core+0x19af/0x33d0 net/core/dev.c:4448
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4486
 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4559
 netif_receive_skb+0xae/0x390 net/core/dev.c:4583
 tun_rx_batched.isra.49+0x5ed/0x860 drivers/net/tun.c:1372
 tun_get_user+0x246b/0x36a0 drivers/net/tun.c:1766
 tun_chr_write_iter+0xbf/0x160 drivers/net/tun.c:1792
 call_write_iter include/linux/fs.h:1770 [inline]
 new_sync_write fs/read_write.c:468 [inline]
 __vfs_write+0x68a/0x970 fs/read_write.c:481
 vfs_write+0x18f/0x510 fs/read_write.c:543
 SYSC_write fs/read_write.c:588 [inline]
 SyS_write+0xef/0x220 fs/read_write.c:580
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x40c341
RSP: 002b:00007fa8277acc10 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 000000000040c341
RDX: 0000000000000036 RSI: 0000000020002000 RDI: 0000000000000015
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000f4240 R11: 0000000000000293 R12: 00000000004ba49c
R13: 00000000ffffffff R14: 0000000000000005 R15: 0000000000000000

Allocated by task 11564:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 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:3690 [inline]
 __kmalloc_node+0x47/0x70 mm/slab.c:3697
 kmalloc_node include/linux/slab.h:550 [inline]
 kvmalloc_node+0x64/0xd0 mm/util.c:397
 kvmalloc include/linux/mm.h:529 [inline]
 kvzalloc include/linux/mm.h:537 [inline]
 alloc_netdev_mqs+0x16d/0xed0 net/core/dev.c:8044
 tun_set_iff drivers/net/tun.c:2245 [inline]
 __tun_chr_ioctl+0x1386/0x3e40 drivers/net/tun.c:2499
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2744
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 11564:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 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:3504 [inline]
 kfree+0xca/0x250 mm/slab.c:3821
 kvfree+0x36/0x60 mm/util.c:416
 netdev_freemem net/core/dev.c:7996 [inline]
 free_netdev+0x2cf/0x360 net/core/dev.c:8158
 tun_set_iff drivers/net/tun.c:2328 [inline]
 __tun_chr_ioctl+0x2df6/0x3e40 drivers/net/tun.c:2499
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2744
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801c73b0b00
 which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 13320 bytes inside of
 16384-byte region [ffff8801c73b0b00, ffff8801c73b4b00)
The buggy address belongs to the page:
page:ffffea00071cec00 count:1 mapcount:0 mapping:ffff8801c73b0b00 index:0x0 compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801c73b0b00 0000000000000000 0000000100000001
raw: ffffea00071d1820 ffffea0007157220 ffff8801dac02200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c73b3e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c73b3e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801c73b3f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8801c73b3f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c73b4000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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