KASAN: vmalloc-out-of-bounds Write in imageblit

Status: upstream: reported on 2026/08/05 13:55
Reported-by: syzbot+802bf88adfebfa7c354f@syzkaller.appspotmail.com
First crash: 21h51m, last: 21h51m
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: vmalloc-out-of-bounds Write in imageblit fbdev 21 syz, C 104 1744d 2038d 20/29 fixed on 2021/11/10 00:50
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (6) prio:high fbdev 21 syz, C 7100 1h30m 276d 0/29 upstream: reported C repro on 2025/11/02 21:10
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (5) fbdev 21 syz, C 1075 280d 331d 29/29 fixed on 2025/10/29 21:02
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (4) fbdev 21 syz, C 3869 335d 715d 29/29 fixed on 2025/09/04 16:57
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (3) fbdev 21 2 1108d 1104d 0/29 auto-obsoleted due to no activity on 2023/10/23 10:50
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (2) fbdev 21 syz, C done 701 1433d 1721d 22/29 fixed on 2023/02/24 13:50
upstream KASAN: vmalloc-out-of-bounds Write in sys_imageblit fbdev 21 syz, C 91 2063d 2430d 0/29 auto-obsoleted due to no activity on 2022/12/09 01:09

Sample crash report:
==================================================================
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 ffffc90003d09fc0 by task syz.4.3141/20291

CPU: 1 PID: 20291 Comm: syz.4.3141 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
 cw_putcs_aligned drivers/video/fbdev/core/fbcon_cw.c:110 [inline]
 cw_putcs+0x15f3/0x18a0 drivers/video/fbdev/core/fbcon_cw.c:158
 fbcon_putcs+0x35c/0x520 drivers/video/fbdev/core/fbcon.c:1301
 do_update_region+0x4e9/0x640 drivers/tty/vt/vt.c:623
 redraw_screen+0xa30/0x1000 drivers/tty/vt/vt.c:983
 vc_do_resize+0x1256/0x17f0 drivers/tty/vt/vt.c:1291
 vt_resizex+0x3f0/0x5a0 drivers/tty/vt/vt_ioctl.c:718
 vt_ioctl+0x1254/0x1f00 drivers/tty/vt/vt_ioctl.c:939
 tty_ioctl+0x91e/0xdc0 drivers/tty/tty_io.c:2779
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 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: 0033:0x7f224c59e019
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:00007f224d3d6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f224c826270 RCX: 00007f224c59e019
RDX: 00002000000006c0 RSI: 000000000000560a RDI: 0000000000000006
RBP: 00007f224c63500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f224c826308 R14: 00007f224c826270 R15: 00007ffc931eecd8
 </TASK>

The buggy address belongs to a vmalloc virtual mapping
Memory state around the buggy address:
 ffffc90003d09e80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90003d09f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90003d09f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                                           ^
 ffffc90003d0a000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90003d0a080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/05 13:55 linux-6.6.y aa0e49877a2e 52aa2820 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: vmalloc-out-of-bounds Write in imageblit
* Struck through repros no longer work on HEAD.