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kernel BUG in ext4_mb_normalize_request

Status: upstream: reported C repro on 2026/03/03 12:10
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+c362a8a885b6f7fab3fa@syzkaller.appspotmail.com
First crash: 50d, last: 2d15h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/03/03 lts (merge base) 6167af934f95 C [report] kernel BUG in ext4_ext_map_blocks
2026/03/03 upstream (ToT) af4e9ef3d784 C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream kernel BUG in ext4_mb_normalize_request (2) ext4 -1 15 26d 115d 0/29 upstream: reported on 2025/12/28 01:12
android-5-10 kernel BUG in ext4_mb_normalize_request -1 C inconclusive 13 14d 125d 0/2 upstream: reported C repro on 2025/12/18 17:49
upstream kernel BUG in ext4_mb_normalize_request ext4 -1 2 274d 351d 0/29 auto-obsoleted due to no activity on 2025/10/30 08:12
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/03/18 10:41 1h36m retest repro android13-5.15-lts report log
2026/03/18 10:41 1h32m retest repro android13-5.15-lts report log

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/mballoc.c:4219!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work

RIP: 0010:ext4_mb_normalize_request+0x192c/0x1990 fs/ext4/mballoc.c:4219
Code: ff e8 48 ea 8b ff 48 c7 c7 a0 b1 89 86 48 89 de 48 8b 55 c8 e8 45 a2 90 00 e9 8e fa ff ff e8 2b ea 8b ff 0f 0b e8 24 ea 8b ff <0f> 0b e8 1d ea 8b ff e9 b7 fb ff ff e8 13 ea 8b ff 0f 0b e8 0c ea
RSP: 0018:ffffc900000873c8 EFLAGS: 00010293
RAX: ffffffff81dddcbc RBX: 0000000000000000 RCX: ffff8881002713c0
RDX: 0000000000000000 RSI: 0000000000000027 RDI: 0000000000000030
RBP: ffffc900000874b0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000010e68 R12: 0000000000000030
R13: 0000000000000027 R14: ffff8881313753f0 R15: 0000000000000027
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4686b25000 CR3: 000000010d6c3000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_mb_new_blocks+0xbfd/0x42c0 fs/ext4/mballoc.c:5779
 ext4_ext_map_blocks+0x1722/0x61e0 fs/ext4/extents.c:4347
 ext4_map_blocks+0x988/0x1b30 fs/ext4/inode.c:674
 ext4_convert_unwritten_extents+0x2b7/0x5f0 fs/ext4/extents.c:4875
 ext4_convert_unwritten_io_end_vec+0x103/0x180 fs/ext4/extents.c:4914
 ext4_end_io_end fs/ext4/page-io.c:186 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:259 [inline]
 ext4_end_io_rsv_work+0x2c1/0x610 fs/ext4/page-io.c:273
 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
 kthread+0x411/0x500 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
Modules linked in:
---[ end trace f87a43cd90fc1c81 ]---
RIP: 0010:ext4_mb_normalize_request+0x192c/0x1990 fs/ext4/mballoc.c:4219
Code: ff e8 48 ea 8b ff 48 c7 c7 a0 b1 89 86 48 89 de 48 8b 55 c8 e8 45 a2 90 00 e9 8e fa ff ff e8 2b ea 8b ff 0f 0b e8 24 ea 8b ff <0f> 0b e8 1d ea 8b ff e9 b7 fb ff ff e8 13 ea 8b ff 0f 0b e8 0c ea
RSP: 0018:ffffc900000873c8 EFLAGS: 00010293
RAX: ffffffff81dddcbc RBX: 0000000000000000 RCX: ffff8881002713c0
RDX: 0000000000000000 RSI: 0000000000000027 RDI: 0000000000000030
RBP: ffffc900000874b0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000010e68 R12: 0000000000000030
R13: 0000000000000027 R14: ffff8881313753f0 R15: 0000000000000027
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4686b25000 CR3: 000000010d6c3000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/20 07:31 android13-5.15-lts 7fad219d720d 303e2802 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
2026/03/04 04:50 android13-5.15-lts e714749f59d3 4180d919 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
2026/03/03 11:58 android13-5.15-lts e714749f59d3 28b83e23 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
2026/04/19 22:01 android13-5.15-lts 7fad219d720d 303e2802 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
2026/03/04 09:18 android13-5.15-lts e714749f59d3 4180d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
2026/03/03 10:51 android13-5.15-lts e714749f59d3 28b83e23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
2026/03/03 10:50 android13-5.15-lts e714749f59d3 28b83e23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
2026/03/03 10:50 android13-5.15-lts e714749f59d3 28b83e23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 kernel BUG in ext4_mb_normalize_request
* Struck through repros no longer work on HEAD.