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BUG: KASAN: vmalloc-out-of-bounds in fast_imageblit drivers/video/fbdev/core/sysimgblt.c:257 [inline]
BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x1ba8/0x25d0 drivers/video/fbdev/core/sysimgblt.c:323
Write of size 4 at addr ffffc90004819000 by task syz.1.136/5035

CPU: 0 PID: 5035 Comm: syz.1.136 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 fast_imageblit drivers/video/fbdev/core/sysimgblt.c:257 [inline]
 sys_imageblit+0x1ba8/0x25d0 drivers/video/fbdev/core/sysimgblt.c:323
 drm_fb_helper_sys_imageblit+0x2e/0x510 drivers/gpu/drm/drm_fb_helper.c:864
 soft_cursor+0x9fd/0xc30 drivers/video/fbdev/core/softcursor.c:74
 bit_cursor+0x16b5/0x1f40 drivers/video/fbdev/core/bitblit.c:409
 hide_cursor+0x7f/0x320 drivers/tty/vt/vt.c:907
 do_con_write+0x1dd/0x6c40 drivers/tty/vt/vt.c:2927
 con_write+0x1f/0x40 drivers/tty/vt/vt.c:3295
 process_output_block drivers/tty/n_tty.c:586 [inline]
 n_tty_write+0xd61/0x11e0 drivers/tty/n_tty.c:2377
 do_tty_write drivers/tty/tty_io.c:1018 [inline]
 file_tty_write+0x4c7/0x840 drivers/tty/tty_io.c:1089
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x482/0x9a0 fs/read_write.c:584
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f35eff9e159
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:00007f35f0eb5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f35f0226270 RCX: 00007f35eff9e159
RDX: 0000000000001006 RSI: 0000200000000e00 RDI: 0000000000000008
RBP: 00007f35f003506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f35f0226308 R14: 00007f35f0226270 R15: 00007ffe2f2211f8
 </TASK>

The buggy address belongs to a 0-page vmalloc region starting at 0xffffc90004519000 allocated at drm_gem_shmem_vmap_locked drivers/gpu/drm/drm_gem_shmem_helper.c:320 [inline]
The buggy address belongs to a 0-page vmalloc region starting at 0xffffc90004519000 allocated at drm_gem_shmem_vmap+0x347/0x4d0 drivers/gpu/drm/drm_gem_shmem_helper.c:367
Memory state around the buggy address:
 ffffc90004818f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90004818f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90004819000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90004819080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004819100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
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