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BUG: KASAN: use-after-free in soft_cursor+0x96b/0xa30 drivers/video/fbdev/core/softcursor.c:61
Read of size 1 at addr ffff888087e0ce36 by task kworker/0:3/5827

CPU: 0 PID: 5827 Comm: kworker/0:3 Not tainted 4.19.147-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+0x22c/0x33e lib/dump_stack.c:118
 print_address_description.cold+0x56/0x25c mm/kasan/report.c:256
 kasan_report_error.cold+0x66/0xb9 mm/kasan/report.c:354
 kasan_report mm/kasan/report.c:412 [inline]
 __asan_report_load1_noabort+0x88/0x90 mm/kasan/report.c:430
 soft_cursor+0x96b/0xa30 drivers/video/fbdev/core/softcursor.c:61
 bit_cursor+0x112a/0x1750 drivers/video/fbdev/core/bitblit.c:377
 fb_flashcursor+0x412/0x530 drivers/video/fbdev/core/fbcon.c:379
 process_one_work+0x796/0x14e0 kernel/workqueue.c:2155
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2298
 kthread+0x33f/0x460 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 7776:
 __do_kmalloc_node mm/slab.c:3689 [inline]
 __kmalloc_node_track_caller+0x4c/0x70 mm/slab.c:3703
 __kmalloc_reserve net/core/skbuff.c:137 [inline]
 __alloc_skb+0xae/0x580 net/core/skbuff.c:205
 alloc_skb include/linux/skbuff.h:995 [inline]
 nlmsg_new include/net/netlink.h:511 [inline]
 rtmsg_ifinfo_build_skb+0x72/0x1a0 net/core/rtnetlink.c:3353
 rollback_registered_many+0x924/0xf00 net/core/dev.c:8192
 unregister_netdevice_many+0x47/0x340 net/core/dev.c:9311
 vti6_exit_batch_net+0x4d7/0x710 net/ipv6/ip6_vti.c:1179
 ops_exit_list+0xf9/0x150 net/core/net_namespace.c:156
 cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553
 process_one_work+0x796/0x14e0 kernel/workqueue.c:2155
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2298
 kthread+0x33f/0x460 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Freed by task 7776:
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcc/0x250 mm/slab.c:3822
 skb_free_head net/core/skbuff.c:554 [inline]
 skb_release_data+0x6ea/0x930 net/core/skbuff.c:574
 skb_release_all net/core/skbuff.c:631 [inline]
 __kfree_skb net/core/skbuff.c:645 [inline]
 consume_skb+0x113/0x3e0 net/core/skbuff.c:705
 netlink_broadcast_filtered+0x319/0xbc0 net/netlink/af_netlink.c:1520
 netlink_broadcast net/netlink/af_netlink.c:1542 [inline]
 nlmsg_multicast include/net/netlink.h:591 [inline]
 nlmsg_notify+0x157/0x1a0 net/netlink/af_netlink.c:2498
 rollback_registered_many+0x9a0/0xf00 net/core/dev.c:8205
 unregister_netdevice_many+0x47/0x340 net/core/dev.c:9311
 vti6_exit_batch_net+0x4d7/0x710 net/ipv6/ip6_vti.c:1179
 ops_exit_list+0xf9/0x150 net/core/net_namespace.c:156
 cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553
 process_one_work+0x796/0x14e0 kernel/workqueue.c:2155
 worker_thread+0x64c/0x1130 kernel/workqueue.c:2298
 kthread+0x33f/0x460 kernel/kthread.c:259
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the object at ffff888087e0c9c0
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1142 bytes inside of
 2048-byte region [ffff888087e0c9c0, ffff888087e0d1c0)
The buggy address belongs to the page:
page:ffffea00021f8300 count:1 mapcount:0 mapping:ffff88812c3f6c40 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea0002836d88 ffffea00013c0d08 ffff88812c3f6c40
raw: 0000000000000000 ffff888087e0c140 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888087e0cd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888087e0cd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888087e0ce00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff888087e0ce80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888087e0cf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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