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BUG: KASAN: use-after-free in fib6_ifdown+0x81e/0x8b0 net/ipv6/route.c:3661
Read of size 1 at addr ffff8801bf90e4bf by task syz-executor2/29085

CPU: 1 PID: 29085 Comm: syz-executor2 Not tainted 4.15.0-rc7+ #187
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:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
 fib6_ifdown+0x81e/0x8b0 net/ipv6/route.c:3661
 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_down_dev net/ipv6/route.c:3698 [inline]
 rt6_disable_ip+0xfd/0x700 net/ipv6/route.c:3703
 addrconf_ifdown+0x14b/0x14f0 net/ipv6/addrconf.c:3595
 addrconf_notify+0x5f8/0x2310 net/ipv6/addrconf.c:3519
 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_set_mtu+0x3c5/0x720 net/core/dev.c:7025
 dev_ifsioc+0x73c/0x9b0 net/core/dev_ioctl.c:264
 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+0x23/0x9a
RIP: 0033:0x452cf9
RSP: 002b:00007f28e4b07c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f28e4b08700 RCX: 0000000000452cf9
RDX: 0000000020dc4000 RSI: 0000000000008922 RDI: 0000000000000014
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a2f7ef R14: 00007f28e4b089c0 R15: 0000000000000000

Allocated by task 27486:
 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
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
 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+0x23/0x9a

Freed by task 27486:
 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:3488 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
 dst_destroy+0x257/0x370 net/core/dst.c:140
 dst_release_immediate+0x4c/0x90 net/core/dst.c:205
 ip6_route_info_create+0x15ac/0x2e20 net/ipv6/route.c:2767
 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+0x23/0x9a

The buggy address belongs to the object at ffff8801bf90e380
 which belongs to the cache ip6_dst_cache of size 320
The buggy address is located 319 bytes inside of
 320-byte region [ffff8801bf90e380, ffff8801bf90e4c0)
The buggy address belongs to the page:
page:ffffea0006fe4380 count:1 mapcount:0 mapping:ffff8801bf90e080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bf90e080 0000000000000000 000000010000000a
raw: ffffea00070f27e0 ffffea00071898a0 ffff8801d3284540 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bf90e380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bf90e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801bf90e480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                                        ^
 ffff8801bf90e500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801bf90e580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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