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BUG: KASAN: use-after-free in fib6_ifup+0x212/0x220 net/ipv6/route.c:3573
Read of size 8 at addr ffff8801a6a23640 by task syz-executor2/10545

CPU: 1 PID: 10545 Comm: syz-executor2 Not tainted 4.15.0-rc7-mm1+ #56
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23b/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 fib6_ifup+0x212/0x220 net/ipv6/route.c:3573
 fib6_clean_node+0x389/0x580 net/ipv6/ip6_fib.c:1912
 fib6_walk_continue+0x46c/0x8a0 net/ipv6/ip6_fib.c:1838
 fib6_walk+0x91/0xf0 net/ipv6/ip6_fib.c:1886
 fib6_clean_tree+0x1e6/0x340 net/ipv6/ip6_fib.c:1963
 __fib6_clean_all+0x1f4/0x3a0 net/ipv6/ip6_fib.c:1979
 fib6_clean_all+0x27/0x30 net/ipv6/ip6_fib.c:1990
 rt6_sync_up+0x15e/0x1c0 net/ipv6/route.c:3592
 addrconf_notify+0x3f6/0x2310 net/ipv6/addrconf.c:3490
 notifier_call_chain+0x136/0x2c0 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+0x32/0x70 net/core/dev.c:1708
 call_netdevice_notifiers net/core/dev.c:1726 [inline]
 __dev_notify_flags+0x15d/0x430 net/core/dev.c:6933
 dev_change_flags+0xf5/0x140 net/core/dev.c:6969
 dev_ifsioc+0x60d/0x9b0 net/core/dev_ioctl.c:257
 dev_ioctl+0x2d7/0xfb0 net/core/dev_ioctl.c:566
 sock_do_ioctl+0x94/0xb0 net/socket.c:965
 sock_ioctl+0x2c2/0x440 net/socket.c:1055
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452cf9
RSP: 002b:00007f584c1fdc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452cf9
RDX: 0000000020334000 RSI: 0000000000008914 RDI: 0000000000000016
RBP: 00000000000003ad R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f38d8
R13: 00000000ffffffff R14: 00007f584c1fe6d4 R15: 0000000000000000

Allocated by task 10116:
 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:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3541
 dst_alloc+0x11f/0x1a0 net/core/dst.c:104
 __ip6_dst_alloc+0x35/0x90 net/ipv6/route.c:361
 ip6_dst_alloc+0x29/0xb0 net/ipv6/route.c:376
 ip6_route_info_create+0x4ff/0x2e20 net/ipv6/route.c:2538
 ip6_route_add+0xa2/0x190 net/ipv6/route.c:2779
 ipv6_route_ioctl+0x4db/0x6b0 net/ipv6/route.c:3299
 inet6_ioctl+0xef/0x1e0 net/ipv6/af_inet6.c:520
 sock_do_ioctl+0x65/0xb0 net/socket.c:958
 sock_ioctl+0x2c2/0x440 net/socket.c:1055
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 10540:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kmem_cache_free+0x86/0x2b0 mm/slab.c:3743
 dst_destroy+0x257/0x370 net/core/dst.c:140
 dst_destroy_rcu+0x16/0x20 net/core/dst.c:153
 __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
 rcu_do_batch kernel/rcu/tree.c:2674 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2933 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2900 [inline]
 rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2917
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801a6a23640
 which belongs to the cache ip6_dst_cache of size 320
The buggy address is located 0 bytes inside of
 320-byte region [ffff8801a6a23640, ffff8801a6a23780)
The buggy address belongs to the page:
page:ffffea00069a88c0 count:1 mapcount:0 mapping:ffff8801a6a23040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801a6a23040 0000000000000000 000000010000000a
raw: ffffea00074afba0 ffffea00075794a0 ffff8801d2d76240 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801a6a23500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801a6a23580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8801a6a23600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                           ^
 ffff8801a6a23680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801a6a23700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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