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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 __internal_add_timer+0x275/0x2d0 kernel/time/timer.c:531
Write of size 8 at addr ffff8801c431c948 by task syz-executor1/32487

CPU: 1 PID: 32487 Comm: syz-executor1 Not tainted 4.14.0-rc1-next-20170920+ #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
netlink: 12 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 5 bytes leftover after parsing attributes in process `syz-executor7'.
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_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]
 __internal_add_timer+0x275/0x2d0 kernel/time/timer.c:531
 internal_add_timer kernel/time/timer.c:573 [inline]
 __mod_timer kernel/time/timer.c:1024 [inline]
 mod_timer kernel/time/timer.c:1071 [inline]
 add_timer+0x60d/0x14d0 kernel/time/timer.c:1092
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1542 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1200 [inline]
 sctp_do_sm+0x3738/0x6dd0 net/sctp/sm_sideeffect.c:1171
 sctp_primitive_ASSOCIATE+0x9d/0xd0 net/sctp/primitive.c:88
 __sctp_connect+0x807/0xc80 net/sctp/socket.c:1207
 sctp_connect+0xb4/0xf0 net/sctp/socket.c:4137
 inet_dgram_connect+0x16b/0x1f0 net/ipv4/af_inet.c:540
 SYSC_connect+0x20a/0x480 net/socket.c:1642
 SyS_connect+0x24/0x30 net/socket.c:1623
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x4520a9
RSP: 002b:00007fb58de27c08 EFLAGS: 00000216 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 00000000004520a9
RDX: 000000000000001c RSI: 0000000020005000 RDI: 0000000000000005
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004bcc68
R13: 00000000ffffffff R14: 0000000000000005 R15: 0000000000000029

Allocated by task 32450:
 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:3689 [inline]
 __kmalloc_node+0x47/0x70 mm/slab.c:3696
 kmalloc_node include/linux/slab.h:535 [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+0x16e/0xed0 net/core/dev.c:8018
 tun_set_iff drivers/net/tun.c:2022 [inline]
 __tun_chr_ioctl+0x12be/0x3d20 drivers/net/tun.c:2276
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2521
 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 32450:
 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:3503 [inline]
 kfree+0xca/0x250 mm/slab.c:3820
 kvfree+0x36/0x60 mm/util.c:416
 netdev_freemem net/core/dev.c:7970 [inline]
 free_netdev+0x2cf/0x360 net/core/dev.c:8132
 tun_set_iff drivers/net/tun.c:2105 [inline]
 __tun_chr_ioctl+0x2cf6/0x3d20 drivers/net/tun.c:2276
 tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:2521
 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 ffff8801c4319540
 which belongs to the cache kmalloc-16384 of size 16384
The buggy address is located 13320 bytes inside of
 16384-byte region [ffff8801c4319540, ffff8801c431d540)
The buggy address belongs to the page:
page:ffffea000710c600 count:1 mapcount:0 mapping:ffff8801c4319540 index:0x0 compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801c4319540 0000000000000000 0000000100000001
raw: ffffea000718ea20 ffffea00072bd020 ffff8801dac02200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c431c800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c431c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801c431c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8801c431c980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c431ca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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