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BUG: KASAN: use-after-free in ex_handler_refcount+0x162/0x1a0 arch/x86/mm/extable.c:49
Write of size 4 at addr ffff88805db99240 by task kworker/u4:6/5135

CPU: 0 PID: 5135 Comm: kworker/u4:6 Not tainted 4.14.170-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x142/0x197 lib/dump_stack.c:58
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
 __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:434
 ex_handler_refcount+0x162/0x1a0 arch/x86/mm/extable.c:49
 fixup_exception+0x8b/0xb9 arch/x86/mm/extable.c:197
 do_trap_no_signal arch/x86/kernel/traps.c:208 [inline]
 do_trap+0x65/0x250 arch/x86/kernel/traps.c:257
 do_error_trap+0x153/0x310 arch/x86/kernel/traps.c:301
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
 invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:963
RIP: 0010:inat_get_avx_attribute+0x635a/0x7ad5
RSP: 0018:ffff8880527e7c60 EFLAGS: 00010283
RAX: ffff88808c97c180 RBX: ffff88805db991c0 RCX: ffff88805db99240
RDX: 0000000000000000 RSI: ffff88808c97ca50 RDI: ffff88809ac166d8
RBP: ffff8880527e7c68 R08: 0000000000004fbc R09: ffffffff89577660
R10: ffff88808c97ca50 R11: ffff88808c97c180 R12: dffffc0000000000
R13: ffff88809ac16540 R14: ffff8880974733a0 R15: ffff888097473360
 l2tp_tunnel_closeall+0x1ef/0x380 net/l2tp/l2tp_core.c:1332
 l2tp_tunnel_del_work+0x64/0x410 net/l2tp/l2tp_core.c:1380
 process_one_work+0x863/0x1600 kernel/workqueue.c:2114
 worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
 kthread+0x319/0x430 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 17521:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
 __do_kmalloc_node mm/slab.c:3682 [inline]
 __kmalloc_node_track_caller+0x51/0x80 mm/slab.c:3696
 __kmalloc_reserve.isra.0+0x40/0xe0 net/core/skbuff.c:137
 __alloc_skb+0xcf/0x500 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:980 [inline]
 alloc_skb_with_frags+0x86/0x4b0 net/core/skbuff.c:5228
 sock_alloc_send_pskb+0x5db/0x740 net/core/sock.c:2078
 sock_alloc_send_skb+0x32/0x40 net/core/sock.c:2095
 mld_newpack+0x1c0/0x7a0 net/ipv6/mcast.c:1585
 add_grhead.isra.0+0x299/0x370 net/ipv6/mcast.c:1691
 add_grec+0x69c/0xef0 net/ipv6/mcast.c:1822
 mld_send_cr net/ipv6/mcast.c:1948 [inline]
 mld_ifc_timer_expire+0x33e/0x7b0 net/ipv6/mcast.c:2455
 call_timer_fn+0x161/0x670 kernel/time/timer.c:1279
 expire_timers kernel/time/timer.c:1318 [inline]
 __run_timers kernel/time/timer.c:1636 [inline]
 __run_timers kernel/time/timer.c:1604 [inline]
 run_timer_softirq+0x5b7/0x1520 kernel/time/timer.c:1649
 __do_softirq+0x244/0x9a0 kernel/softirq.c:288

Freed by task 17521:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcc/0x270 mm/slab.c:3815
 skb_free_head+0x8b/0xb0 net/core/skbuff.c:554
 skb_release_data+0x543/0x7c0 net/core/skbuff.c:574
 skb_release_all+0x4d/0x60 net/core/skbuff.c:631
 __kfree_skb net/core/skbuff.c:645 [inline]
 kfree_skb+0xb5/0x350 net/core/skbuff.c:663
 ip6_mc_input+0x614/0xa70 net/ipv6/ip6_input.c:417
 dst_input include/net/dst.h:468 [inline]
 ip6_rcv_finish+0x23f/0x7a0 net/ipv6/ip6_input.c:71
 NF_HOOK include/linux/netfilter.h:250 [inline]
 NF_HOOK include/linux/netfilter.h:244 [inline]
 ipv6_rcv+0xf11/0x1da0 net/ipv6/ip6_input.c:218
 __netif_receive_skb_core+0x1ebe/0x2cb0 net/core/dev.c:4477
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4515
 process_backlog+0x21f/0x730 net/core/dev.c:5197
 napi_poll net/core/dev.c:5598 [inline]
 net_rx_action+0x490/0xf80 net/core/dev.c:5664
 __do_softirq+0x244/0x9a0 kernel/softirq.c:288

The buggy address belongs to the object at ffff88805db991c0
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 128 bytes inside of
 2048-byte region [ffff88805db991c0, ffff88805db999c0)
The buggy address belongs to the page:
page:ffffea000176e600 count:1 mapcount:0 mapping:ffff88805db980c0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88805db980c0 0000000000000000 0000000100000003
raw: ffffea00015fc420 ffffea00017aeea0 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88805db99100: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88805db99180: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff88805db99200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88805db99280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805db99300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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