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BUG: KASAN: stack-out-of-bounds in fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline]
BUG: KASAN: stack-out-of-bounds in bitfill drivers/video/fbdev/core/fb_fillrect.h:139 [inline]
BUG: KASAN: stack-out-of-bounds in fb_fillrect_static drivers/video/fbdev/core/fb_fillrect.h:219 [inline]
BUG: KASAN: stack-out-of-bounds in fb_fillrect drivers/video/fbdev/core/fb_fillrect.h:278 [inline]
BUG: KASAN: stack-out-of-bounds in sys_fillrect+0x173d/0x1910 drivers/video/fbdev/core/sysfillrect.c:24
Write of size 8 at addr ffffc90003f7f798 by task syz.1.1063/15712

CPU: 1 UID: 0 PID: 15712 Comm: syz.1.1063 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x156/0x4c9 mm/kasan/report.c:482
 kasan_report+0xdf/0x1e0 mm/kasan/report.c:595
 fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline]
 bitfill drivers/video/fbdev/core/fb_fillrect.h:139 [inline]
 fb_fillrect_static drivers/video/fbdev/core/fb_fillrect.h:219 [inline]
 fb_fillrect drivers/video/fbdev/core/fb_fillrect.h:278 [inline]
 sys_fillrect+0x173d/0x1910 drivers/video/fbdev/core/sysfillrect.c:24
 drm_fbdev_shmem_defio_fillrect+0x22/0x140 drivers/gpu/drm/drm_fbdev_shmem.c:39
 bit_clear+0x17d/0x220 drivers/video/fbdev/core/bitblit.c:73
 __fbcon_clear+0x633/0x760 drivers/video/fbdev/core/fbcon.c:1327
 fbcon_scroll+0x48b/0x650 drivers/video/fbdev/core/fbcon.c:1881
 con_scroll+0x464/0x690 drivers/tty/vt/vt.c:582
 csi_M drivers/tty/vt/vt.c:2134 [inline]
 csi_ECMA drivers/tty/vt/vt.c:2553 [inline]
 do_con_trol drivers/tty/vt/vt.c:2727 [inline]
 do_con_write+0x6883/0x8540 drivers/tty/vt/vt.c:3222
 con_write+0x23/0xb0 drivers/tty/vt/vt.c:3558
 process_output_block drivers/tty/n_tty.c:557 [inline]
 n_tty_write+0x44f/0x12d0 drivers/tty/n_tty.c:2366
 iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
 file_tty_write.isra.0+0x4d2/0x890 drivers/tty/tty_io.c:1081
 tty_write drivers/tty/tty_io.c:1102 [inline]
 redirected_tty_write drivers/tty/tty_io.c:1125 [inline]
 redirected_tty_write+0xd4/0x120 drivers/tty/tty_io.c:1105
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4085b9c139
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4086a3e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f4085e15fa0 RCX: 00007f4085b9c139
RDX: 000000000000fdef RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007f4085c327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4085e16038 R14: 00007f4085e15fa0 R15: 00007fff6e140698
 </TASK>

The buggy address belongs to a vmalloc virtual mapping
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7a747
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x29c2(GFP_NOWAIT|__GFP_HIGHMEM|__GFP_IO|__GFP_FS|__GFP_ZERO), pid 5172, tgid 5172 (start-stop-daem), ts 30576542313, free_ts 28444386422
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1888
 prep_new_page mm/page_alloc.c:1896 [inline]
 get_page_from_freelist+0x111d/0x3140 mm/page_alloc.c:3961
 __alloc_frozen_pages_noprof+0x27c/0x2ba0 mm/page_alloc.c:5249
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2485
 alloc_frozen_pages_noprof mm/mempolicy.c:2556 [inline]
 alloc_pages_noprof+0x131/0x390 mm/mempolicy.c:2576
 vm_area_alloc_pages mm/vmalloc.c:3662 [inline]
 __vmalloc_area_node mm/vmalloc.c:3876 [inline]
 __vmalloc_node_range_noprof+0xe5c/0x1530 mm/vmalloc.c:4064
 __vmalloc_node_noprof+0xad/0xf0 mm/vmalloc.c:4124
 alloc_thread_stack_node kernel/fork.c:355 [inline]
 dup_task_struct kernel/fork.c:924 [inline]
 copy_process+0x5ec/0x7a10 kernel/fork.c:2050
 kernel_clone+0xfc/0x9a0 kernel/fork.c:2654
 __do_sys_vfork+0x9f/0xe0 kernel/fork.c:2757
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1432 [inline]
 __free_frozen_pages+0x7ca/0x10a0 mm/page_alloc.c:2977
 __free_pages mm/page_alloc.c:5368 [inline]
 free_contig_range+0xde/0x1d0 mm/page_alloc.c:7372
 debug_vm_pgtable_free_huge_page mm/debug_vm_pgtable.c:980 [inline]
 destroy_args+0xa8/0x7a0 mm/debug_vm_pgtable.c:993
 debug_vm_pgtable+0x1b66/0x34c0 mm/debug_vm_pgtable.c:1368
 do_one_initcall+0x11d/0x760 init/main.c:1382
 do_initcall_level init/main.c:1444 [inline]
 do_initcalls init/main.c:1460 [inline]
 do_basic_setup init/main.c:1479 [inline]
 kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692
 kernel_init+0x1f/0x1e0 init/main.c:1582
 ret_from_fork+0x754/0xd80 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:
 ffffc90003f7f680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003f7f700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90003f7f780: 00 00 00 f1 f1 f1 f1 00 00 f3 f3 00 00 00 00 00
                            ^
 ffffc90003f7f800: 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00
 ffffc90003f7f880: 00 00 00 00 00 00 00 00 00 f3 f3 f3 f3 f3 00 00
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