syzbot


kernel BUG in ext4_mb_use_inode_pa

Status: upstream: reported C repro on 2026/02/22 04:22
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+79def8a4693e93b11ce1@syzkaller.appspotmail.com
First crash: 15h09m, last: 15h09m
Bug presence (2)
Date Name Commit Repro Result
2026/02/22 lts (merge base) e45d5d41c134 C [report] kernel BUG in ext4_ext_insert_extent
2026/02/22 upstream (ToT) 32a92f8c8932 C Didn't crash
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream kernel BUG in ext4_mb_use_inode_pa ext4 -1 C error done 2 1237d 1237d 22/29 fixed on 2023/02/24 13:50
upstream kernel BUG in ext4_mb_use_inode_pa (2) ext4 -1 C error 279 12d 563d 0/29 upstream: reported C repro on 2024/08/08 04:33

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/mballoc.c:4374!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 519 Comm: syz.0.38 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:ext4_mb_use_inode_pa+0x6d1/0x730 fs/ext4/mballoc.c:4374
Code: 4c 89 ff e8 11 0b ca ff 48 ba 00 00 00 00 00 fc ff df e9 be fa ff ff e8 ad dc 8a ff 0f 0b e8 a6 dc 8a ff 0f 0b e8 9f dc 8a ff <0f> 0b e8 98 dc 8a ff 0f 0b 48 8b 4d d0 80 e1 07 80 c1 03 38 c1 0f
RSP: 0018:ffffc90000b46a60 EFLAGS: 00010293
RAX: ffffffff81def061 RBX: 00000000ffffffff RCX: ffff88811ad9cf00
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000005
RBP: ffffc90000b46ae8 R08: ffff88811851e000 R09: 1ffff11026571a06
R10: dffffc0000000000 R11: ffffed1026571a07 R12: 1ffff11026571a0a
R13: ffff888132b8d050 R14: 0000000000000080 R15: 0000000000000006
FS:  00007f08f4b8f6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000021000 CR3: 00000001134e4000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_mb_use_preallocated+0xb3b/0xcf0 fs/ext4/mballoc.c:4472
 ext4_mb_new_blocks+0x551/0x42c0 fs/ext4/mballoc.c:5779
 ext4_ext_map_blocks+0x1722/0x61e0 fs/ext4/extents.c:4341
 ext4_map_blocks+0x988/0x1b30 fs/ext4/inode.c:674
 _ext4_get_block+0x1ea/0x540 fs/ext4/inode.c:817
 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:848
 ext4_block_write_begin+0x563/0x1160 fs/ext4/inode.c:1102
 ext4_write_begin+0x65a/0x12e0 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x321/0xbf0 fs/ext4/inode.c:2988
 generic_perform_write+0x2b7/0x690 mm/filemap.c:3870
 ext4_buffered_write_iter+0x4ed/0x670 fs/ext4/file.c:270
 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: 0033:0x7f08f4d2c629
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:00007f08f4b8f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f08f4fa5fa0 RCX: 00007f08f4d2c629
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007f08f4dc2b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f08f4fa6038 R14: 00007f08f4fa5fa0 R15: 00007ffc49dca8e8
 </TASK>
Modules linked in:
---[ end trace c69241bde114a50b ]---
RIP: 0010:ext4_mb_use_inode_pa+0x6d1/0x730 fs/ext4/mballoc.c:4374
Code: 4c 89 ff e8 11 0b ca ff 48 ba 00 00 00 00 00 fc ff df e9 be fa ff ff e8 ad dc 8a ff 0f 0b e8 a6 dc 8a ff 0f 0b e8 9f dc 8a ff <0f> 0b e8 98 dc 8a ff 0f 0b 48 8b 4d d0 80 e1 07 80 c1 03 38 c1 0f
RSP: 0018:ffffc90000b46a60 EFLAGS: 00010293
RAX: ffffffff81def061 RBX: 00000000ffffffff RCX: ffff88811ad9cf00
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000005
RBP: ffffc90000b46ae8 R08: ffff88811851e000 R09: 1ffff11026571a06
R10: dffffc0000000000 R11: ffffed1026571a07 R12: 1ffff11026571a0a
R13: ffff888132b8d050 R14: 0000000000000080 R15: 0000000000000006
FS:  00007f08f4b8f6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000021000 CR3: 00000001134e4000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/22 04:21 android13-5.15-lts 13d6d33696ef 6e7b5511 .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_use_inode_pa
* Struck through repros no longer work on HEAD.