syzbot


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: 3d22h, last: 2d23h
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 7 10d 69d 0/29 upstream: reported on 2025/12/28 01:12
android-5-10 kernel BUG in ext4_mb_normalize_request -1 C inconclusive 12 1d09h 78d 0/2 upstream: reported C repro on 2025/12/18 17:49
upstream kernel BUG in ext4_mb_normalize_request ext4 -1 2 228d 305d 0/29 auto-obsoleted due to no activity on 2025/10/30 08:12

Sample crash report:
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 118 with max blocks 2 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost
------------[ cut here ]------------
kernel BUG at fs/ext4/mballoc.c:4258!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 388 Comm: syz.2.22 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:ext4_mb_normalize_request+0x1944/0x1990 fs/ext4/mballoc.c:4258
Code: 00 e9 8e fa ff ff e8 4b eb 8b ff 0f 0b e8 44 eb 8b ff 0f 0b e8 3d eb 8b ff e9 b7 fb ff ff e8 33 eb 8b ff 0f 0b e8 2c eb 8b ff <0f> 0b e8 25 eb 8b ff 0f 0b e8 1e eb 8b ff 48 8b 45 80 42 80 3c 28
RSP: 0018:ffffc9000403eaa8 EFLAGS: 00010293
RAX: ffffffff81dde1d4 RBX: 0000000000000070 RCX: ffff888112260000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffffc9000403eb90 R08: ffff88812ec5750f R09: 1ffff11025d8aea1
R10: dffffc0000000000 R11: ffffed1025d8aea2 R12: 000000000000004a
R13: dffffc0000000000 R14: 0000000000000000 R15: 000000000000004a
FS:  00007fc880ae16c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000034000 CR3: 000000010638b000 CR4: 00000000003506a0
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:5781
 ext4_ext_map_blocks+0x1722/0x61e0 fs/ext4/extents.c:4341
 ext4_map_blocks+0x988/0x1b30 fs/ext4/inode.c:674
 ext4_convert_unwritten_extents+0x2b7/0x5f0 fs/ext4/extents.c:4869
 ext4_convert_unwritten_io_end_vec+0x103/0x180 fs/ext4/extents.c:4908
 ext4_put_io_end+0xc4/0x260 fs/ext4/page-io.c:307
 ext4_writepages+0xfa0/0x3090 fs/ext4/inode.c:2875
 do_writepages+0x473/0x6c0 mm/page-writeback.c:2388
 filemap_fdatawrite_wbc+0x1f4/0x250 mm/filemap.c:409
 __filemap_fdatawrite_range mm/filemap.c:442 [inline]
 file_write_and_wait_range+0x14d/0x220 mm/filemap.c:819
 ext4_sync_file+0x1a9/0xa10 fs/ext4/fsync.c:151
 vfs_fsync_range+0x190/0x1a0 fs/sync.c:188
 generic_write_sync include/linux/fs.h:3038 [inline]
 ext4_buffered_write_iter+0x5d0/0x670 fs/ext4/file.c:277
 ext4_file_write_iter+0x440/0x1540 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2212 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x835/0xfd0 fs/read_write.c:594
 ksys_pwrite64 fs/read_write.c:701 [inline]
 __do_sys_pwrite64 fs/read_write.c:711 [inline]
 __se_sys_pwrite64 fs/read_write.c:708 [inline]
 __x64_sys_pwrite64+0x197/0x220 fs/read_write.c:708
 x64_sys_call+0xa6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:19
 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: 0033:0x7fc880c7e799
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:00007fc880ae1028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007fc880ef7fa0 RCX: 00007fc880c7e799
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000006
RBP: 00007fc880d14bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc880ef8038 R14: 00007fc880ef7fa0 R15: 00007fff7fe1c348
 </TASK>
Modules linked in:
---[ end trace 49c968bf1d47393b ]---
RIP: 0010:ext4_mb_normalize_request+0x1944/0x1990 fs/ext4/mballoc.c:4258
Code: 00 e9 8e fa ff ff e8 4b eb 8b ff 0f 0b e8 44 eb 8b ff 0f 0b e8 3d eb 8b ff e9 b7 fb ff ff e8 33 eb 8b ff 0f 0b e8 2c eb 8b ff <0f> 0b e8 25 eb 8b ff 0f 0b e8 1e eb 8b ff 48 8b 45 80 42 80 3c 28
RSP: 0018:ffffc9000403eaa8 EFLAGS: 00010293
RAX: ffffffff81dde1d4 RBX: 0000000000000070 RCX: ffff888112260000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffffc9000403eb90 R08: ffff88812ec5750f R09: 1ffff11025d8aea1
R10: dffffc0000000000 R11: ffffed1025d8aea2 R12: 000000000000004a
R13: dffffc0000000000 R14: 0000000000000000 R15: 000000000000004a
FS:  00007fc880ae16c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc880ccbe80 CR3: 000000010638b000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
2026/03/04 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.