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BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0xff5/0x1e40
Write of size 8 at addr ffffc90004b29500 by task syz.9.10159/21502

CPU: 1 UID: 0 PID: 21502 Comm: syz.9.10159 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_address_description+0x55/0x1e0
 print_report+0x58/0x70
 kasan_report+0x117/0x150
 sys_imageblit+0xff5/0x1e40
 drm_fbdev_shmem_defio_imageblit+0x2c/0x110
 soft_cursor+0xa0e/0xc40
 bit_cursor+0x11e5/0x19c0
 fbcon_scroll+0x2bc/0x7c0
 con_scroll+0x783/0xa10
 csi_ECMA+0x486/0x6850
 do_con_write+0x41ae/0x5500
 con_write+0x27/0x290
 n_tty_write+0xd49/0x11e0
 file_tty_write+0x50d/0x9f0
 do_iter_readv_writev+0x612/0x8c0
 vfs_writev+0x343/0x990
 do_writev+0x154/0x2e0
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8b67d9e159
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:00007f8b68beb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f8b68025fa0 RCX: 00007f8b67d9e159
RDX: 0000000000000001 RSI: 00002000000025c0 RDI: 0000000000000003
RBP: 00007f8b67e35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8b68026038 R14: 00007f8b68025fa0 R15: 00007ffd1e061e78
 </TASK>

The buggy address belongs to a vmalloc virtual mapping
Memory state around the buggy address:
 ffffc90004b29400: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004b29480: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90004b29500: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90004b29580: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004b29600: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
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