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

Status: upstream: reported on 2026/08/21 23:50
Reported-by: syzbot+4cb5341ba3296c868cf6@syzkaller.appspotmail.com
First crash: 1d17h, last: 1d17h
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: unable to handle kernel paging request in bitfill_aligned (2) fbdev 21 syz, C inconclusive done 26 1697d 2104d 20/29 fixed on 2022/05/13 11:13
upstream KASAN: vmalloc-out-of-bounds Write in bitfill_aligned fbdev 21 syz, C 475 2219d 2453d 15/29 fixed on 2020/09/21 20:54
upstream BUG: unable to handle kernel paging request in bitfill_aligned (4) fbdev 8 8 542d 623d 0/29 auto-obsoleted due to no activity on 2025/06/07 17:05
linux-4.14 BUG: unable to handle kernel paging request in bitfill_aligned 8 1 1466d 1466d 0/1 auto-obsoleted due to no activity on 2022/12/16 16:52
linux-4.19 BUG: unable to handle kernel paging request in bitfill_aligned 8 syz, C error 11 1287d 1717d 0/1 upstream: reported C repro on 2021/12/10 10:17
upstream BUG: unable to handle kernel paging request in bitfill_aligned (3) fbdev 8 syz, C unreliable 11 1461d 1504d 22/29 fixed on 2023/02/24 13:50
linux-6.1 BUG: unable to handle kernel paging request in bitfill_aligned 8 6 1d09h 8d15h 0/3 upstream: reported on 2026/08/15 01:29

Sample crash report:
==================================================================
BUG: KASAN: vmalloc-out-of-bounds in bitfill_aligned+0x316/0x730 drivers/video/fbdev/core/sysfillrect.c:54
Write of size 8 at addr ffffc90004780000 by task syz.3.325/5527

CPU: 1 PID: 5527 Comm: syz.3.325 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
 bitfill_aligned+0x316/0x730 drivers/video/fbdev/core/sysfillrect.c:54
 sys_fillrect+0x600/0x800 drivers/video/fbdev/core/sysfillrect.c:291
 drm_fb_helper_sys_fillrect+0x2e/0x510 drivers/gpu/drm/drm_fb_helper.c:763
 bit_clear+0x15f/0x1f0 drivers/video/fbdev/core/bitblit.c:73
 __fbcon_clear+0x596/0xa30 drivers/video/fbdev/core/fbcon.c:1248
 fbcon_scroll+0x3a6/0x690 drivers/video/fbdev/core/fbcon.c:1751
 con_scroll+0x50e/0x7a0 drivers/tty/vt/vt.c:630
 csi_M+0xa8/0x140 drivers/tty/vt/vt.c:2055
 do_con_trol drivers/tty/vt/vt.c:2463 [inline]
 do_con_write+0x4291/0x6c40 drivers/tty/vt/vt.c:2951
 con_write+0x1f/0x40 drivers/tty/vt/vt.c:3295
 process_output_block drivers/tty/n_tty.c:592 [inline]
 n_tty_write+0xd19/0x1220 drivers/tty/n_tty.c:2339
 do_tty_write drivers/tty/tty_io.c:1038 [inline]
 file_tty_write+0x50c/0x8a0 drivers/tty/tty_io.c:1110
 call_write_iter include/linux/fs.h:2173 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 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: 0033:0x7fdc5301a0d9
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:00007fdc51272028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fdc532a1fa0 RCX: 00007fdc5301a0d9
RDX: 0000000000001006 RSI: 0000200000001040 RDI: 0000000000000004
RBP: 00007fdc530b1024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdc532a2038 R14: 00007fdc532a1fa0 R15: 00007ffc3e2e4808
 </TASK>


Memory state around the buggy address:
 ffffc9000477ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc9000477ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90004780000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90004780080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004780100: 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
2026/08/21 23:49 linux-5.15.y 0eb903b5b519 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: vmalloc-out-of-bounds Write in bitfill_aligned
* Struck through repros no longer work on HEAD.