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BUG: KASAN: slab-out-of-bounds in soft_cursor+0x3d8/0xd80 drivers/video/fbdev/core/softcursor.c:70
Read of size 776 at addr ffff88804ec3eb68 by task syz.1.1832/12569

CPU: 0 UID: 0 PID: 12569 Comm: syz.1.1832 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 soft_cursor+0x3d8/0xd80 drivers/video/fbdev/core/softcursor.c:70
 bit_cursor+0x16d0/0x1f80 drivers/video/fbdev/core/bitblit.c:370
 hide_cursor+0xd8/0x480 drivers/tty/vt/vt.c:855
 update_region+0x1c1/0x490 drivers/tty/vt/vt.c:641
 vcs_write+0xd65/0x1260 drivers/tty/vt/vc_screen.c:685
 vfs_write+0x27e/0xb30 fs/read_write.c:684
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd1f3d8eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd1f4c93038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd1f3fe6090 RCX: 00007fd1f3d8eec9
RDX: 0000000000000007 RSI: 0000200000000100 RDI: 0000000000000005
RBP: 00007fd1f3e11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd1f3fe6128 R14: 00007fd1f3fe6090 R15: 00007ffe6d15ae28
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4ec00
head: order:6 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f8(unknown)
raw: 00fff00000000040 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000f8000000 0000000000000000
head: 00fff00000000040 0000000000000000 dead000000000122 0000000000000000
head: 0000000000000000 0000000000000000 00000000f8000000 0000000000000000
head: 00fff00000000006 ffffea00013b0001 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000040
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 6, migratetype Unmovable, gfp_mask 0x140cc0(GFP_USER|__GFP_COMP), pid 7344, tgid 7343 (syz.1.427), ts 189179272278, free_ts 161245834729
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1850
 prep_new_page mm/page_alloc.c:1858 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3884
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 ___kmalloc_large_node+0x5f/0x1b0 mm/slub.c:5543
 __kmalloc_large_node_noprof+0x18/0x90 mm/slub.c:5574
 __do_kmalloc_node mm/slub.c:5590 [inline]
 __kmalloc_noprof+0x4bd/0x7f0 mm/slub.c:5614
 kmalloc_noprof include/linux/slab.h:961 [inline]
 fbcon_set_font+0x54d/0xec0 drivers/video/fbdev/core/fbcon.c:2536
 con_font_set drivers/tty/vt/vt.c:4919 [inline]
 con_font_op+0xc08/0xfd0 drivers/tty/vt/vt.c:4959
 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:472 [inline]
 vt_ioctl+0x1a89/0x1f20 drivers/tty/vt/vt_ioctl.c:743
 tty_ioctl+0x929/0xde0 drivers/tty/tty_io.c:2792
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 12 tgid 12 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 free_unref_folios+0xdb3/0x14f0 mm/page_alloc.c:2963
 folios_put_refs+0x584/0x670 mm/swap.c:1002
 release_pages+0x4b4/0x520 mm/swap.c:1042
 io_free_region+0xb4/0x270 io_uring/memmap.c:102
 io_rings_free io_uring/io_uring.c:2782 [inline]
 io_ring_ctx_free+0x278/0x4e0 io_uring/io_uring.c:2877
 io_ring_exit_work+0x8c4/0x930 io_uring/io_uring.c:3099
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff88804ec3ea00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 ffff88804ec3ea80: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
>ffff88804ec3eb00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
                                                          ^
 ffff88804ec3eb80: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 ffff88804ec3ec00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
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