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BUG: KASAN: use-after-free in fbcon_cursor+0x8d7/0xc00 drivers/video/fbdev/core/fbcon.c:1389
Read of size 2 at addr ffff888218898a18 by task syz-executor.0/15037

CPU: 0 PID: 15037 Comm: syz-executor.0 Not tainted 5.7.0-rc5-syzkaller #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+0x1e9/0x30e lib/dump_stack.c:118
 print_address_description+0x74/0x5c0 mm/kasan/report.c:382
 __kasan_report+0x103/0x1a0 mm/kasan/report.c:511
 kasan_report+0x4d/0x80 mm/kasan/common.c:625

Allocated by task 1:
 save_stack mm/kasan/common.c:49 [inline]
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc+0x114/0x160 mm/kasan/common.c:495
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc+0x24b/0x330 mm/slab.c:3665
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc+0x1d/0x40 include/linux/slab.h:669
 vc_do_resize+0x2a0/0x1ce0 drivers/tty/vt/vt.c:1217
 fbcon_init+0x119e/0x1e60 drivers/video/fbdev/core/fbcon.c:1218
 visual_init+0x2b4/0x570 drivers/tty/vt/vt.c:1069
 do_bind_con_driver+0x887/0x1370 drivers/tty/vt/vt.c:3566
 do_take_over_console+0x5aa/0x730 drivers/tty/vt/vt.c:4146
 do_fbcon_takeover drivers/video/fbdev/core/fbcon.c:588 [inline]
 fbcon_fb_registered+0x36f/0x650 drivers/video/fbdev/core/fbcon.c:3261
 do_register_framebuffer drivers/video/fbdev/core/fbmem.c:1664 [inline]
 register_framebuffer+0x6d6/0x950 drivers/video/fbdev/core/fbmem.c:1832
 vga16fb_probe+0x69f/0xa20 drivers/video/fbdev/vga16fb.c:1373
 platform_drv_probe+0xcd/0x150 drivers/base/platform.c:735
 really_probe+0x761/0xf60 drivers/base/dd.c:524
 driver_probe_device+0xe6/0x230 drivers/base/dd.c:697
 bus_for_each_drv+0x108/0x170 drivers/base/bus.c:431
 __device_attach+0x20c/0x3a0 drivers/base/dd.c:870
 bus_probe_device+0xb8/0x1f0 drivers/base/bus.c:491
 device_add+0x1828/0x1ba0 drivers/base/core.c:2538
 platform_device_add+0x4ad/0x6e0 drivers/base/platform.c:585
 vga16fb_init+0xee/0x13e drivers/video/fbdev/vga16fb.c:1431
 do_one_initcall+0x14b/0x350 init/main.c:1194
 do_initcall_level+0x101/0x14c init/main.c:1267
 do_initcalls+0x59/0x9b init/main.c:1283
 kernel_init_freeable+0x2fa/0x418 init/main.c:1487
 kernel_init+0xd/0x290 init/main.c:1394
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351

Freed by task 15037:
 save_stack mm/kasan/common.c:49 [inline]
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0x125/0x190 mm/kasan/common.c:456
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 vc_do_resize+0xf63/0x1ce0 drivers/tty/vt/vt.c:1291
 vt_ioctl+0x3178/0x3eb0 drivers/tty/vt/vt_ioctl.c:901
 tty_ioctl+0xee4/0x15c0 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl fs/ioctl.c:771 [inline]
 __do_sys_ioctl fs/ioctl.c:780 [inline]
 __se_sys_ioctl+0xf9/0x160 fs/ioctl.c:778
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff888218898000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 2584 bytes inside of
 8192-byte region [ffff888218898000, ffff88821889a000)
The buggy address belongs to the page:
page:ffffea0008622600 refcount:1 mapcount:0 mapping:00000000629b5d06 index:0x0 head:ffffea0008622600 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x57ffe0000010200(slab|head)
raw: 057ffe0000010200 ffffea0008621308 ffffea00085fc708 ffff8880aa4021c0
raw: 0000000000000000 ffff888218898000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888218898900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888218898980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888218898a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888218898a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888218898b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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