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

Status: upstream: reported on 2026/08/06 13:30
Reported-by: syzbot+23839731b8735c36866b@syzkaller.appspotmail.com
First crash: 1d13h, last: 1d00h
▶ ▼ Similar bugs (9)
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 1746d 2039d 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 7189 22m 278d 0/29 upstream: reported C repro on 2025/11/02 21:10
linux-6.1 KASAN: vmalloc-out-of-bounds Write in imageblit 21 1 21h39m 21h38m 0/3 upstream: reported on 2026/08/07 05:50
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (5) fbdev 21 syz, C 1075 282d 333d 29/29 fixed on 2025/10/29 21:02
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (4) fbdev 21 syz, C 3869 337d 716d 29/29 fixed on 2025/09/04 16:57
upstream KASAN: vmalloc-out-of-bounds Write in imageblit (3) fbdev 21 2 1109d 1105d 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 1434d 1722d 22/29 fixed on 2023/02/24 13:50
linux-6.6 KASAN: vmalloc-out-of-bounds Write in imageblit 21 3 5h15m 2d13h 0/2 upstream: reported on 2026/08/05 13:55
upstream KASAN: vmalloc-out-of-bounds Write in sys_imageblit fbdev 21 syz, C 91 2065d 2432d 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:276 [inline]
BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x2110/0x25d0 drivers/video/fbdev/core/sysimgblt.c:323
Write of size 4 at addr ffffc90004941ff8 by task syz.1.1709/9546

CPU: 0 PID: 9546 Comm: syz.1.1709 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 fast_imageblit drivers/video/fbdev/core/sysimgblt.c:276 [inline]
 sys_imageblit+0x2110/0x25d0 drivers/video/fbdev/core/sysimgblt.c:323
 drm_fb_helper_sys_imageblit+0x2e/0x510 drivers/gpu/drm/drm_fb_helper.c:793
 cw_putcs_aligned drivers/video/fbdev/core/fbcon_cw.c:110 [inline]
 cw_putcs+0x15ef/0x18a0 drivers/video/fbdev/core/fbcon_cw.c:158
 fbcon_putcs+0x2c8/0x450 drivers/video/fbdev/core/fbcon.c:1265
 do_update_region+0x4e5/0x640 drivers/tty/vt/vt.c:676
 redraw_screen+0xa2c/0x1000 drivers/tty/vt/vt.c:1035
 vc_do_resize+0x122c/0x17b0 drivers/tty/vt/vt.c:1342
 fbcon_do_set_font+0xc6e/0x1cd0 drivers/video/fbdev/core/fbcon.c:2412
 con_font_set drivers/tty/vt/vt.c:4669 [inline]
 con_font_op+0xace/0xdc0 drivers/tty/vt/vt.c:4715
 vt_k_ioctl drivers/tty/vt/vt_ioctl.c:474 [inline]
 vt_ioctl+0x162f/0x1cb0 drivers/tty/vt/vt_ioctl.c:752
 tty_ioctl+0x848/0xc30 drivers/tty/tty_io.c:2810
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f48ba5d20d9
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:00007f48b87e8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f48ba85a180 RCX: 00007f48ba5d20d9
RDX: 00002000000001c0 RSI: 0000000000004b72 RDI: 0000000000000007
RBP: 00007f48ba669024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f48ba85a218 R14: 00007f48ba85a180 R15: 00007ffc61eccee8
 </TASK>


Memory state around the buggy address:
 ffffc90004941e80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004941f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90004941f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                                                                ^
 ffffc90004942000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004942080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/07 03:22 linux-5.15.y 9c7634c60784 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: vmalloc-out-of-bounds Write in imageblit
2026/08/07 03:22 linux-5.15.y 9c7634c60784 c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: vmalloc-out-of-bounds Write in imageblit
2026/08/06 13:29 linux-5.15.y 6e2fd6534337 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: vmalloc-out-of-bounds Write in imageblit
* Struck through repros no longer work on HEAD.