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BUG: KASAN: use-after-free in fib6_remove_prefsrc+0x3c6/0x470 net/ipv6/route.c:3417
Read of size 8 at addr ffff8801c090c500 by task syz-executor6/7624

CPU: 1 PID: 7624 Comm: syz-executor6 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_remove_prefsrc+0x3c6/0x470 net/ipv6/route.c:3417
 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_remove_prefsrc+0x165/0x210 net/ipv6/route.c:3438
 ipv6_del_addr+0x4d1/0xb70 net/ipv6/addrconf.c:1264
 inet6_addr_del+0x2ff/0x5b0 net/ipv6/addrconf.c:2928
 addrconf_del_ifaddr+0x139/0x1c0 net/ipv6/addrconf.c:2973
 inet6_ioctl+0x86/0x1e0 net/ipv6/af_inet6.c:525
 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
RIP: 0033:0x452cf9
RSP: 002b:00007f4d6e786c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bf58 RCX: 0000000000452cf9
RDX: 0000000020000000 RSI: 0000000000008936 RDI: 0000000000000014
RBP: 000000000000016d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f02d8
R13: 00000000ffffffff R14: 00007f4d6e7876d4 R15: 0000000000000002

Allocated by task 7614:
 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
 addrconf_prefix_route+0x3fa/0x630 net/ipv6/addrconf.c:2321
 inet6_addr_add+0x2b4/0x390 net/ipv6/addrconf.c:2875
 addrconf_add_ifaddr+0x145/0x1d0 net/ipv6/addrconf.c:2954
 inet6_ioctl+0x111/0x1e0 net/ipv6/af_inet6.c:523
 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 4804:
 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 ffff8801c090c500
 which belongs to the cache ip6_dst_cache of size 320
The buggy address is located 0 bytes inside of
 320-byte region [ffff8801c090c500, ffff8801c090c640)
The buggy address belongs to the page:
page:ffffea0007024300 count:1 mapcount:0 mapping:ffff8801c090c080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c090c080 0000000000000000 000000010000000a
raw: ffffea0007547620 ffffea00076559e0 ffff8801d2d6a3c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c090c400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c090c480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8801c090c500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8801c090c580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c090c600: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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