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BUG: KASAN: use-after-free in fbcon_cursor+0x409/0x570 drivers/video/fbdev/core/fbcon.c:1389
Read of size 2 at addr ffff8880a18cc28c by task syz-executor.0/9794

CPU: 1 PID: 9794 Comm: syz-executor.0 Not tainted 5.6.0-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+0x12d/0x187 lib/dump_stack.c:118
 print_address_description.constprop.8.cold.10+0x9/0x31d mm/kasan/report.c:382
 __kasan_report.cold.11+0x37/0x4e mm/kasan/report.c:511
 kasan_report+0x38/0x50 mm/kasan/common.c:625
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/generic_report.c:144
 fbcon_cursor+0x409/0x570 drivers/video/fbdev/core/fbcon.c:1389
 fbcon_scrolldelta+0x525/0xf00 drivers/video/fbdev/core/fbcon.c:2886
 fbcon_set_origin+0x16/0x20 drivers/video/fbdev/core/fbcon.c:2937
 set_origin+0xcc/0x390 drivers/tty/vt/vt.c:920
 vc_do_resize+0x8ec/0x12b0 drivers/tty/vt/vt.c:1288
 vc_resize+0x3d/0x60 drivers/tty/vt/vt.c:1328
 vt_ioctl+0x35e/0x24c0 drivers/tty/vt/vt_ioctl.c:850
 tty_ioctl+0x45b/0x12f0 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0xc1/0x110 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:770
 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45a909
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f56a8cbac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a909
RDX: 0000000020000000 RSI: 0000000000005609 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f56a8cbb6d4
R13: 00000000004c7009 R14: 00000000004dd670 R15: 00000000ffffffff

Allocated by task 9786:
 save_stack+0x21/0x50 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc.constprop.17+0xc7/0xd0 mm/kasan/common.c:495
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:509
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc+0x164/0x790 mm/slab.c:3665
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 vc_do_resize+0x1de/0x12b0 drivers/tty/vt/vt.c:1211
 vc_resize+0x3d/0x60 drivers/tty/vt/vt.c:1328
 vt_ioctl+0x35e/0x24c0 drivers/tty/vt/vt_ioctl.c:850
 tty_ioctl+0x45b/0x12f0 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0xc1/0x110 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:770
 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 9794:
 save_stack+0x21/0x50 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:456
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:465
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x108/0x2c0 mm/slab.c:3757
 vc_do_resize+0x889/0x12b0 drivers/tty/vt/vt.c:1285
 vc_resize+0x3d/0x60 drivers/tty/vt/vt.c:1328
 vt_ioctl+0x35e/0x24c0 drivers/tty/vt/vt_ioctl.c:850
 tty_ioctl+0x45b/0x12f0 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0xc1/0x110 fs/ioctl.c:763
 __do_sys_ioctl fs/ioctl.c:772 [inline]
 __se_sys_ioctl fs/ioctl.c:770 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:770
 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff8880a18cc280
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 12 bytes inside of
 32-byte region [ffff8880a18cc280, ffff8880a18cc2a0)
The buggy address belongs to the page:
page:ffffea0002863300 refcount:1 mapcount:0 mapping:0000000034afa877 index:0xffff8880a18ccfc1
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000292fd48 ffffea00029d6ac8 ffff8880aa4001c0
raw: ffff8880a18ccfc1 ffff8880a18cc000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a18cc180: fb fb fb fb fc fc fc fc 00 00 01 fc fc fc fc fc
 ffff8880a18cc200: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8880a18cc280: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
                      ^
 ffff8880a18cc300: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8880a18cc380: 00 00 01 fc fc fc fc fc fb fb fb fb fc fc fc fc
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