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BUG: KASAN: slab-out-of-bounds in soft_cursor+0x96b/0xa30 drivers/video/fbdev/core/softcursor.c:61
Read of size 1 at addr ffff88809621a510 by task kworker/0:1/12

CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.9.0-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+0x198/0x1fd lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 soft_cursor+0x96b/0xa30 drivers/video/fbdev/core/softcursor.c:61
 bit_cursor+0xcfe/0x1720 drivers/video/fbdev/core/bitblit.c:377
 fb_flashcursor+0x38b/0x430 drivers/video/fbdev/core/fbcon.c:397
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 2257:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 __do_kmalloc mm/slab.c:3655 [inline]
 __kmalloc+0x1b0/0x360 mm/slab.c:3664
 kmalloc include/linux/slab.h:559 [inline]
 fbcon_set_font+0x363/0x9b0 drivers/video/fbdev/core/fbcon.c:2496
 con_font_set drivers/tty/vt/vt.c:4663 [inline]
 con_font_op+0xd26/0x1140 drivers/tty/vt/vt.c:4728
 vt_io_ioctl drivers/tty/vt/vt_ioctl.c:595 [inline]
 vt_ioctl+0x1ce7/0x2e90 drivers/tty/vt/vt_ioctl.c:856
 tty_ioctl+0x1019/0x15f0 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Last call_rcu():
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_record_aux_stack+0x82/0xb0 mm/kasan/generic.c:346
 __call_rcu kernel/rcu/tree.c:2894 [inline]
 call_rcu+0x15e/0x7c0 kernel/rcu/tree.c:2968
 inetdev_destroy net/ipv4/devinet.c:328 [inline]
 inetdev_event+0xcc5/0x14fd net/ipv4/devinet.c:1599
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:83
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:2033
 call_netdevice_notifiers_extack net/core/dev.c:2045 [inline]
 call_netdevice_notifiers net/core/dev.c:2059 [inline]
 rollback_registered_many+0x77a/0x1250 net/core/dev.c:9284
 unregister_netdevice_many.part.0+0x1a/0x2f0 net/core/dev.c:10429
 unregister_netdevice_many net/core/dev.c:10428 [inline]
 default_device_exit_batch+0x30c/0x3d0 net/core/dev.c:10912
 ops_exit_list+0x10d/0x160 net/core/net_namespace.c:189
 cleanup_net+0x4ea/0xa00 net/core/net_namespace.c:603
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the object at ffff88809621a400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 272 bytes inside of
 512-byte region [ffff88809621a400, ffff88809621a600)
The buggy address belongs to the page:
page:000000000f3bb7bb refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x9621a
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000278b008 ffffea000183e388 ffff8880aa040600
raw: 0000000000000000 ffff88809621a000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809621a400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88809621a480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88809621a500: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                         ^
 ffff88809621a580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88809621a600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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