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BUG: KASAN: slab-out-of-bounds in soft_cursor+0x62c/0xdb0 drivers/video/fbdev/core/softcursor.c:61
Read of size 1 at addr ffff8880a05c1746 by task kworker/0:4/2594

CPU: 0 PID: 2594 Comm: kworker/0:4 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_power_efficient fb_flashcursor
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1f0/0x31e lib/dump_stack.c:118
 print_address_description+0x66/0x5a0 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 soft_cursor+0x62c/0xdb0 drivers/video/fbdev/core/softcursor.c:61
 bit_cursor+0x178a/0x2180 drivers/video/fbdev/core/bitblit.c:386
 fb_flashcursor+0x725/0xa10 drivers/video/fbdev/core/fbcon.c:417
 process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
 worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415
 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Allocated by task 19631:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494
 kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 ipv6_add_addr+0x3a4/0x16f0 net/ipv6/addrconf.c:1081
 add_addr+0x13b/0x4a0 net/ipv6/addrconf.c:3048
 sit_add_v4_addrs net/ipv6/addrconf.c:3107 [inline]
 addrconf_sit_config net/ipv6/addrconf.c:3358 [inline]
 addrconf_notify+0x216f/0x3a60 net/ipv6/addrconf.c:3551
 notifier_call_chain kernel/notifier.c:83 [inline]
 __raw_notifier_call_chain kernel/notifier.c:361 [inline]
 raw_notifier_call_chain+0xe7/0x170 kernel/notifier.c:368
 __dev_notify_flags+0x253/0x4d0 net/core/dev.c:2027
 rtnl_configure_link+0x21f/0x340 net/core/rtnetlink.c:3028
 __rtnl_newlink net/core/rtnetlink.c:3357 [inline]
 rtnl_newlink+0x154a/0x1bf0 net/core/rtnetlink.c:3397
 rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5460
 netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2469
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0x519/0x800 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmsg+0x2b1/0x360 net/socket.c:2439
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 18800:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 skb_release_all net/core/skbuff.c:664 [inline]
 __kfree_skb+0x56/0x1c0 net/core/skbuff.c:678
 udpv6_queue_rcv_one_skb+0x8c2/0x11c0 arch/x86/include/asm/atomic.h:97
 udp6_unicast_rcv_skb net/ipv6/udp.c:831 [inline]
 __udp6_lib_rcv+0x10f2/0x2900 net/ipv6/udp.c:915
 ip6_protocol_deliver_rcu+0x9ab/0x1680 net/ipv6/ip6_input.c:433
 ip6_input_finish net/ipv6/ip6_input.c:474 [inline]
 NF_HOOK include/linux/netfilter.h:307 [inline]
 ip6_input+0x10b/0x190 net/ipv6/ip6_input.c:483
 __netif_receive_skb_one_core net/core/dev.c:5281 [inline]
 __netif_receive_skb+0x164/0x3c0 net/core/dev.c:5395
 process_backlog+0x4f8/0x930 net/core/dev.c:6239
 napi_poll net/core/dev.c:6684 [inline]
 net_rx_action+0x615/0x10e0 net/core/dev.c:6752
 __do_softirq+0x268/0x80c kernel/softirq.c:292

The buggy address belongs to the object at ffff8880a05c1400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 326 bytes to the right of
 512-byte region [ffff8880a05c1400, ffff8880a05c1600)
The buggy address belongs to the page:
page:ffffea0002817040 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000269c908 ffffea0002788088 ffff8880aa400a80
raw: 0000000000000000 ffff8880a05c1000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a05c1600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a05c1680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a05c1700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                           ^
 ffff8880a05c1780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a05c1800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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