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BUG: KASAN: slab-out-of-bounds in fib6_nh_get_excptn_bucket+0x198/0x1b0 net/ipv6/route.c:1595
Read of size 8 at addr ffff88808eb0c1f8 by task ksoftirqd/0/9

CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.4.0-rc6+ #0
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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:634
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 fib6_nh_get_excptn_bucket+0x198/0x1b0 net/ipv6/route.c:1595
 fib6_nh_flush_exceptions+0x37/0x2d0 net/ipv6/route.c:1723
 fib6_nh_release+0x84/0x3a0 net/ipv6/route.c:3505
 fib6_info_destroy_rcu+0x11e/0x160 net/ipv6/ip6_fib.c:174
 __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
 rcu_do_batch kernel/rcu/tree.c:2157 [inline]
 rcu_core+0x581/0x1560 kernel/rcu/tree.c:2377
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2386
 __do_softirq+0x262/0x98c kernel/softirq.c:292
 run_ksoftirqd kernel/softirq.c:603 [inline]
 run_ksoftirqd+0x8e/0x110 kernel/softirq.c:595
 smpboot_thread_fn+0x6a3/0xa40 kernel/smpboot.c:165
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 6588:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:510 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
 kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3550
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:690 [inline]
 fib6_info_alloc+0xb6/0x1b0 net/ipv6/ip6_fib.c:154
 ip6_route_info_create+0x2fe/0x1530 net/ipv6/route.c:3607
 ip6_route_add+0x27/0xc0 net/ipv6/route.c:3699
 inet6_rtm_newroute+0x16c/0x180 net/ipv6/route.c:5267
 rtnetlink_rcv_msg+0x463/0xb00 net/core/rtnetlink.c:5387
 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
 rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5405
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x531/0x710 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x8a5/0xd60 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:657
 ___sys_sendmsg+0x803/0x920 net/socket.c:2311
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2356
 __do_sys_sendmsg net/socket.c:2365 [inline]
 __se_sys_sendmsg net/socket.c:2363 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2363
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 14883:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
 __cache_free mm/slab.c:3425 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3756
 ext4_ext_map_blocks+0x912/0x3ac0 fs/ext4/extents.c:4562
 ext4_map_blocks+0x52b/0x17e0 fs/ext4/inode.c:640
 mpage_map_one_extent fs/ext4/inode.c:2468 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2517 [inline]
 ext4_writepages+0x1924/0x2e80 fs/ext4/inode.c:2869
 do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
 __writeback_single_inode+0x136/0x1400 fs/fs-writeback.c:1452
 writeback_sb_inodes+0x596/0xf20 fs/fs-writeback.c:1716
 __writeback_inodes_wb+0xc3/0x260 fs/fs-writeback.c:1785
 wb_writeback+0x910/0xd90 fs/fs-writeback.c:1894
 wb_check_start_all fs/fs-writeback.c:2018 [inline]
 wb_do_writeback fs/fs-writeback.c:2044 [inline]
 wb_workfn+0xb4c/0x1220 fs/fs-writeback.c:2078
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff88808eb0c100
 which belongs to the cache kmalloc-192 of size 192
The buggy address is located 56 bytes to the right of
 192-byte region [ffff88808eb0c100, ffff88808eb0c1c0)
The buggy address belongs to the page:
page:ffffea00023ac300 refcount:1 mapcount:0 mapping:ffff8880aa400000 index:0xffff88808eb0c200
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea00026c0188 ffffea0001b6be48 ffff8880aa400000
raw: ffff88808eb0c200 ffff88808eb0c000 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808eb0c080: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88808eb0c100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88808eb0c180: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
                                                                ^
 ffff88808eb0c200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808eb0c280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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