syzbot


kernel BUG in ext4_mb_use_inode_pa

Status: premoderation: reported syz repro on 2026/03/09 22:43
Reported-by: syzbot+c73f9bd1bd5bad1ff804@syzkaller.appspotmail.com
First crash: 2d10h, last: 2d09h
Similar bugs (4)
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 1255d 1255d 22/29 fixed on 2023/02/24 13:50
upstream kernel BUG in ext4_mb_use_inode_pa (2) ext4 -1 C error 280 14d 581d 0/29 upstream: reported C repro on 2024/08/08 04:33
android-5-15 kernel BUG in ext4_mb_use_inode_pa origin:lts -1 C 5 1d17h 18d 0/2 upstream: reported C repro on 2026/02/22 04:22
linux-6.1 kernel BUG in ext4_mb_use_inode_pa -1 syz 1 23h32m 23h32m 0/3 upstream: reported syz repro on 2026/03/11 09:28

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/mballoc.c:3845!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 719 Comm: syz.1.65 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+0x511/0x520 fs/ext4/mballoc.c:3845
Code: c1 03 38 c1 0f 8c 1b fe ff ff 4c 89 ff e8 07 5d ca ff e9 0e fe ff ff e8 5d dc 8f ff 0f 0b e8 56 dc 8f ff 0f 0b e8 4f dc 8f ff <0f> 0b e8 48 dc 8f ff 0f 0b 66 0f 1f 44 00 00 55 48 89 e5 41 57 41
RSP: 0018:ffffc9000348ea78 EFLAGS: 00010293
RAX: ffffffff81d4d701 RBX: 00000000ffffffff RCX: ffff88810ba9e2c0
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000004
RBP: ffffc9000348eae8 R08: ffff888128e7b967 R09: 1ffff110251cf72c
R10: dffffc0000000000 R11: ffffed10251cf72d R12: 0000000000000005
R13: dffffc0000000000 R14: 1ffff110251cf730 R15: ffff888128e7b980
FS:  00007f5c91a006c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000240bf CR3: 0000000111054000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ext4_mb_use_preallocated+0xacc/0xc80 fs/ext4/mballoc.c:3943
 ext4_mb_new_blocks+0x5df/0x4340 fs/ext4/mballoc.c:5247
 ext4_ext_map_blocks+0x1679/0x5dd0 fs/ext4/extents.c:4341
 ext4_map_blocks+0x985/0x1bd0 fs/ext4/inode.c:674
 _ext4_get_block+0x1d1/0x4e0 fs/ext4/inode.c:817
 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:848
 ext4_block_write_begin+0x573/0x1340 fs/ext4/inode.c:1101
 ext4_write_begin+0x67e/0x1690 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x478/0xf10 fs/ext4/inode.c:3033
 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509
 ext4_buffered_write_iter+0x4b8/0x640 fs/ext4/file.c:271
 ext4_file_write_iter+0x53f/0x1980 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x758/0xdc0 fs/read_write.c:605
 ksys_pwrite64 fs/read_write.c:712 [inline]
 __do_sys_pwrite64 fs/read_write.c:722 [inline]
 __se_sys_pwrite64 fs/read_write.c:719 [inline]
 __x64_sys_pwrite64+0x197/0x220 fs/read_write.c:719
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f5c91b9d799
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:00007f5c91a00028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f5c91e16fa0 RCX: 00007f5c91b9d799
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000006
RBP: 00007f5c91c33bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5c91e17038 R14: 00007f5c91e16fa0 R15: 00007ffddca2ad38
Modules linked in:
---[ end trace eef115b04c90d159 ]---
RIP: 0010:ext4_mb_use_inode_pa+0x511/0x520 fs/ext4/mballoc.c:3845
Code: c1 03 38 c1 0f 8c 1b fe ff ff 4c 89 ff e8 07 5d ca ff e9 0e fe ff ff e8 5d dc 8f ff 0f 0b e8 56 dc 8f ff 0f 0b e8 4f dc 8f ff <0f> 0b e8 48 dc 8f ff 0f 0b 66 0f 1f 44 00 00 55 48 89 e5 41 57 41
RSP: 0018:ffffc9000348ea78 EFLAGS: 00010293
RAX: ffffffff81d4d701 RBX: 00000000ffffffff RCX: ffff88810ba9e2c0
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000004
RBP: ffffc9000348eae8 R08: ffff888128e7b967 R09: 1ffff110251cf72c
R10: dffffc0000000000 R11: ffffed10251cf72d R12: 0000000000000005
R13: dffffc0000000000 R14: 1ffff110251cf730 R15: ffff888128e7b980
FS:  00007f5c91a006c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000240bf CR3: 0000000111054000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/09 23:19 android13-5.10-lts 9136079e403a 176bead5 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_mb_use_inode_pa
2026/03/09 22:42 android13-5.10-lts 9136079e403a 176bead5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_mb_use_inode_pa
* Struck through repros no longer work on HEAD.