==================================================================
BUG: KASAN: slab-out-of-bounds in soft_cursor+0x95d/0xa40 drivers/video/fbdev/core/softcursor.c:61
Read of size 1 at addr ffff88808e7cec98 by task kworker/1:1/32088

CPU: 1 PID: 32088 Comm: kworker/1:1 Not tainted 4.14.184-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:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2b9 mm/kasan/report.c:393
 soft_cursor+0x95d/0xa40 drivers/video/fbdev/core/softcursor.c:61
 bit_cursor+0x1072/0x1660 drivers/video/fbdev/core/bitblit.c:386
 fb_flashcursor+0x360/0x400 drivers/video/fbdev/core/fbcon.c:393
 process_one_work+0x7c0/0x14c0 kernel/workqueue.c:2116
 worker_thread+0x5d7/0x1080 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 14694:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc.part.0+0x4f/0xd0 mm/kasan/kasan.c:551
 __do_kmalloc mm/slab.c:3720 [inline]
 __kmalloc+0x15a/0x400 mm/slab.c:3729
 kmalloc include/linux/slab.h:493 [inline]
 fbcon_set_font+0x2f8/0x7c0 drivers/video/fbdev/core/fbcon.c:2621
 con_font_set drivers/tty/vt/vt.c:4182 [inline]
 con_font_op+0xb73/0xf70 drivers/tty/vt/vt.c:4247
 vt_ioctl+0x736/0x1f20 drivers/tty/vt/vt_ioctl.c:928
 tty_ioctl+0x6c9/0x1220 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xfe0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 17:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xaf/0x190 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcb/0x260 mm/slab.c:3815
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2699 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline]
 rcu_process_callbacks+0x78d/0x1180 kernel/rcu/tree.c:2946
 __do_softirq+0x254/0x9bf kernel/softirq.c:288

The buggy address belongs to the object at ffff88808e7ceac0
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 472 bytes inside of
 512-byte region [ffff88808e7ceac0, ffff88808e7cecc0)
The buggy address belongs to the page:
page:ffffea000239f380 count:1 mapcount:0 mapping:ffff88808e7ce0c0 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff88808e7ce0c0 0000000000000000 0000000100000006
raw: ffffea00022ba6e0 ffffea00027f8ce0 ffff8880aa800940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808e7ceb80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
 ffff88808e7cec00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808e7cec80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff88808e7ced00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff88808e7ced80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================