syzbot
kernel BUG in ext4_mb_normalize_request
Status:
upstream: reported C repro on 2025/12/18 17:49
Reported-by: syzbot+16dfafdbe48358333904@syzkaller.appspotmail.com
First crash: 219d, last: 108d
Fix bisection:
the issue occurs on the latest tested release
(bisect log)
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Last patch testing requests (10)
Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/mballoc.c:3729!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 49 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
RIP: 0010:ext4_mb_normalize_request+0x1291/0x12e0 fs/ext4/mballoc.c:3729
Code: ff ff 48 8b 7d a8 e8 ae 27 cb ff e9 6b fc ff ff e8 b4 a6 90 ff 0f 0b e8 ad a6 90 ff 0f 0b e8 a6 a6 90 ff 0f 0b e8 9f a6 90 ff <0f> 0b e8 98 a6 90 ff 0f 0b e8 91 a6 90 ff 48 8b 85 78 ff ff ff 42
RSP: 0018:ffffc900009e7410 EFLAGS: 00010293
RAX: ffffffff81d40fb1 RBX: 0000000000000060 RCX: ffff888101ffbb40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffffc900009e74f0 R08: ffff888129c1e86f R09: 1ffff11025383d0d
R10: dffffc0000000000 R11: ffffed1025383d0e R12: ffff888120f2cb60
R13: dffffc0000000000 R14: 0000000000000000 R15: 000000000000001f
FS: 0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000340bf CR3: 000000010ac21000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
ext4_mb_new_blocks+0xc31/0x4340 fs/ext4/mballoc.c:5249
ext4_ext_map_blocks+0x1679/0x5dd0 fs/ext4/extents.c:4335
ext4_map_blocks+0x985/0x1bd0 fs/ext4/inode.c:674
ext4_convert_unwritten_extents+0x227/0x400 fs/ext4/extents.c:4862
ext4_convert_unwritten_io_end_vec+0x103/0x180 fs/ext4/extents.c:4901
ext4_end_io_end fs/ext4/page-io.c:189 [inline]
ext4_do_flush_completed_IO fs/ext4/page-io.c:262 [inline]
ext4_end_io_rsv_work+0x2c1/0x610 fs/ext4/page-io.c:276
process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
worker_thread+0xa6a/0x13c0 kernel/workqueue.c:2447
kthread+0x346/0x3d0 kernel/kthread.c:313
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
Modules linked in:
---[ end trace 61c386cae9c7a2cb ]---
RIP: 0010:ext4_mb_normalize_request+0x1291/0x12e0 fs/ext4/mballoc.c:3729
Code: ff ff 48 8b 7d a8 e8 ae 27 cb ff e9 6b fc ff ff e8 b4 a6 90 ff 0f 0b e8 ad a6 90 ff 0f 0b e8 a6 a6 90 ff 0f 0b e8 9f a6 90 ff <0f> 0b e8 98 a6 90 ff 0f 0b e8 91 a6 90 ff 48 8b 85 78 ff ff ff 42
RSP: 0018:ffffc900009e7410 EFLAGS: 00010293
RAX: ffffffff81d40fb1 RBX: 0000000000000060 RCX: ffff888101ffbb40
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffffc900009e74f0 R08: ffff888129c1e86f R09: 1ffff11025383d0d
R10: dffffc0000000000 R11: ffffed1025383d0e R12: ffff888120f2cb60
R13: dffffc0000000000 R14: 0000000000000000 R15: 000000000000001f
FS: 0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f36fe8c7ff8 CR3: 000000010ed2d000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
* Struck through repros no longer work on HEAD.