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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+0x1bac/0x25d0 drivers/video/fbdev/core/sysimgblt.c:323
Write of size 4 at addr ffffc90003ba11a0 by task syz.0.6706/24644

CPU: 0 PID: 24644 Comm: syz.0.6706 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 fast_imageblit drivers/video/fbdev/core/sysimgblt.c:257 [inline]
 sys_imageblit+0x1bac/0x25d0 drivers/video/fbdev/core/sysimgblt.c:323
 drm_fbdev_generic_defio_imageblit+0x2c/0x110 drivers/gpu/drm/drm_fbdev_generic.c:37
 soft_cursor+0xa01/0xc30 drivers/video/fbdev/core/softcursor.c:74
 bit_cursor+0x16b2/0x1f10 drivers/video/fbdev/core/bitblit.c:404
 set_cursor drivers/tty/vt/vt.c:868 [inline]
 con_flush_chars+0x1fa/0x280 drivers/tty/vt/vt.c:3318
 con_write+0x2e/0x40 drivers/tty/vt/vt.c:3246
 process_output_block drivers/tty/n_tty.c:580 [inline]
 n_tty_write+0xd3d/0x11e0 drivers/tty/n_tty.c:2395
 iterate_tty_write drivers/tty/tty_io.c:1017 [inline]
 file_tty_write+0x529/0x960 drivers/tty/tty_io.c:1088
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x474/0x9a0 fs/read_write.c:584
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fbc2b79e0d9
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:00007fbc2c72f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fbc2ba25fa0 RCX: 00007fbc2b79e0d9
RDX: 0000000000001006 RSI: 00002000000012c0 RDI: 0000000000000004
RBP: 00007fbc2b835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbc2ba26038 R14: 00007fbc2ba25fa0 R15: 00007ffd4970d428
 </TASK>

The buggy address belongs to a 0-page vmalloc region starting at 0xffffc90003ba2000 allocated at drm_gem_shmem_vmap+0x3c4/0x650 drivers/gpu/drm/drm_gem_shmem_helper.c:340
Memory state around the buggy address:
 ffffc90003ba1080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90003ba1100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90003ba1180: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                               ^
 ffffc90003ba1200: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90003ba1280: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
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