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BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
BUG: KASAN: use-after-free in refcount_sub_and_test+0x9a/0x350 lib/refcount.c:179
Read of size 4 at addr ffff8801ae43ca44 by task syz-executor3/1241

CPU: 0 PID: 1241 Comm: syz-executor3 Not tainted 4.18.0-rc7+ #172
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
 atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
 refcount_sub_and_test+0x9a/0x350 lib/refcount.c:179
 refcount_dec_and_test+0x1a/0x20 lib/refcount.c:212
 fib6_metrics_release+0x4f/0x90 net/ipv6/ip6_fib.c:178
 fib6_drop_pcpu_from net/ipv6/ip6_fib.c:899 [inline]
 fib6_purge_rt+0x5ec/0x7f0 net/ipv6/ip6_fib.c:934
 fib6_del_route net/ipv6/ip6_fib.c:1784 [inline]
 fib6_del+0xc11/0x1310 net/ipv6/ip6_fib.c:1815
 fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976
 fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899
 fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947
 fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024
 __fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040
 fib6_clean_all+0x27/0x30 net/ipv6/ip6_fib.c:2051
 rt6_sync_down_dev net/ipv6/route.c:4083 [inline]
 rt6_disable_ip+0x111/0x7e0 net/ipv6/route.c:4088
 addrconf_ifdown+0x16f/0x1670 net/ipv6/addrconf.c:3650
 addrconf_notify+0x6e9/0x27f0 net/ipv6/addrconf.c:3575
 notifier_call_chain+0x180/0x390 kernel/notifier.c:93
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
 call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1735
 call_netdevice_notifiers net/core/dev.c:1753 [inline]
 dev_close_many+0x447/0x8d0 net/core/dev.c:1505
 rollback_registered_many+0x52b/0xef0 net/core/dev.c:7452
 rollback_registered+0x1e9/0x420 net/core/dev.c:7517
 unregister_netdevice_queue+0x32f/0x660 net/core/dev.c:8561
 unregister_netdevice include/linux/netdevice.h:2548 [inline]
 __tun_detach+0x11d1/0x15e0 drivers/net/tun.c:727
 tun_detach drivers/net/tun.c:744 [inline]
 tun_chr_close+0xe3/0x180 drivers/net/tun.c:3271
 __fput+0x355/0x8b0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x1b08/0x2750 kernel/exit.c:865
 do_group_exit+0x177/0x440 kernel/exit.c:968
 get_signal+0x88e/0x1970 kernel/signal.c:2468
 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e0/0x370 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x456a09
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007f4f1ee3acf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 0000000000930148 RCX: 0000000000456a09
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000930148
RBP: 0000000000930140 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000093014c
R13: 0000000000a3fc8f R14: 00007f4f1ee3b9c0 R15: 0000000000000001

Allocated by task 32703:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
 kmalloc include/linux/slab.h:513 [inline]
 kzalloc include/linux/slab.h:707 [inline]
 fib6_metric_set+0x163/0x2c0 net/ipv6/ip6_fib.c:645
 fib6_add_rt2node+0xe36/0x27f0 net/ipv6/ip6_fib.c:1000
 fib6_add+0xaae/0x14d0 net/ipv6/ip6_fib.c:1308
 __ip6_ins_rt+0x54/0x80 net/ipv6/route.c:1163
 ip6_route_add+0x6d/0xc0 net/ipv6/route.c:3171
 addrconf_prefix_route.isra.48+0x51d/0x720 net/ipv6/addrconf.c:2347
 inet6_addr_modify net/ipv6/addrconf.c:4627 [inline]
 inet6_rtm_newaddr+0x112e/0x1b50 net/ipv6/addrconf.c:4743
 rtnetlink_rcv_msg+0x46e/0xc30 net/core/rtnetlink.c:4665
 netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2453
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4683
 netlink_unicast_kernel net/netlink/af_netlink.c:1315 [inline]
 netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1341
 netlink_sendmsg+0xa18/0xfd0 net/netlink/af_netlink.c:1906
 sock_sendmsg_nosec net/socket.c:642 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:652
 ___sys_sendmsg+0x7fd/0x930 net/socket.c:2126
 __sys_sendmsg+0x11d/0x290 net/socket.c:2164
 __do_sys_sendmsg net/socket.c:2173 [inline]
 __se_sys_sendmsg net/socket.c:2171 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2171
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 1241:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xd9/0x260 mm/slab.c:3813
 fib6_metrics_release+0x77/0x90 net/ipv6/ip6_fib.c:179
 fib6_drop_pcpu_from net/ipv6/ip6_fib.c:899 [inline]
 fib6_purge_rt+0x5ec/0x7f0 net/ipv6/ip6_fib.c:934
 fib6_del_route net/ipv6/ip6_fib.c:1784 [inline]
 fib6_del+0xc11/0x1310 net/ipv6/ip6_fib.c:1815
 fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976
 fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899
 fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947
 fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024
 __fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040
 fib6_clean_all+0x27/0x30 net/ipv6/ip6_fib.c:2051
 rt6_sync_down_dev net/ipv6/route.c:4083 [inline]
 rt6_disable_ip+0x111/0x7e0 net/ipv6/route.c:4088
 addrconf_ifdown+0x16f/0x1670 net/ipv6/addrconf.c:3650
 addrconf_notify+0x6e9/0x27f0 net/ipv6/addrconf.c:3575
 notifier_call_chain+0x180/0x390 kernel/notifier.c:93
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
 call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1735
 call_netdevice_notifiers net/core/dev.c:1753 [inline]
 dev_close_many+0x447/0x8d0 net/core/dev.c:1505
 rollback_registered_many+0x52b/0xef0 net/core/dev.c:7452
 rollback_registered+0x1e9/0x420 net/core/dev.c:7517
 unregister_netdevice_queue+0x32f/0x660 net/core/dev.c:8561
 unregister_netdevice include/linux/netdevice.h:2548 [inline]
 __tun_detach+0x11d1/0x15e0 drivers/net/tun.c:727
 tun_detach drivers/net/tun.c:744 [inline]
 tun_chr_close+0xe3/0x180 drivers/net/tun.c:3271
 __fput+0x355/0x8b0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x1b08/0x2750 kernel/exit.c:865
 do_group_exit+0x177/0x440 kernel/exit.c:968
 get_signal+0x88e/0x1970 kernel/signal.c:2468
 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e0/0x370 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801ae43ca00
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 68 bytes inside of
 96-byte region [ffff8801ae43ca00, ffff8801ae43ca60)
The buggy address belongs to the page:
page:ffffea0006b90f00 count:1 mapcount:0 mapping:ffff8801dac004c0 index:0xffff8801ae43cc00
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0006c44148 ffffea0006c0b188 ffff8801dac004c0
raw: ffff8801ae43cc00 ffff8801ae43c000 000000010000000a 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ae43c900: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8801ae43c980: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff8801ae43ca00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                           ^
 ffff8801ae43ca80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8801ae43cb00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
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