kernel BUG in ext4_mb_use_inode_pa

Status: upstream: reported syz repro on 2026/03/11 09:28
Reported-by: syzbot+d5a5b04ce0161e7eb1f9@syzkaller.appspotmail.com
First crash: 151d, last: 151d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/07/26 upstream (ToT) 3dab139d4795 syz Failed due to an error; will retry later
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 kernel BUG in ext4_mb_use_inode_pa -1 syz done 2 122d 152d 0/2 auto-obsoleted due to no activity on 2026/07/08 01:45
upstream kernel BUG in ext4_mb_use_inode_pa ext4 -1 syz, C error done 2 1406d 1405d 22/29 fixed on 2023/02/24 13:50
upstream kernel BUG in ext4_mb_use_inode_pa (2) ext4 -1 syz, C error 416 2d00h 731d 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 syz, C error 6 111d 168d 0/2 upstream: reported C repro on 2026/02/22 04:22

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/mballoc.c:4360!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 5593 Comm: syz.1.237 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : ext4_mb_use_inode_pa+0x550/0x5a0 fs/ext4/mballoc.c:4360
lr : ext4_mb_use_inode_pa+0x550/0x5a0 fs/ext4/mballoc.c:4360
sp : ffff800023de6b40
x29: ffff800023de6b90 x28: ffff0000f68ebaa0 x27: 0000000000000003
x26: 0000000000000201 x25: ffff0000f68eba64 x24: 1fffe0001ed1d74c
x23: dfff800000000000 x22: 00000000ffffffff x21: 1fffe0001c0b1249
x20: 0000000000000002 x19: ffff0000e0589248 x18: ffff800011b8bf60
x17: 1fffe00033ea877e x16: ffff8000082ee970 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe0001c0b1246 x12: 0000000000ff0100
x11: ff00800008dbeef4 x10: 0000000000000000 x9 : ffff800008dbeef4
x8 : ffff0000d4cdb780 x7 : ffff800008dac99c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff0000f68eba5c
x2 : ffff0000f68eba60 x1 : 0000000000000003 x0 : 0000000000000002
Call trace:
 ext4_mb_use_inode_pa+0x550/0x5a0 fs/ext4/mballoc.c:4360
 ext4_mb_use_preallocated+0xc00/0xe34 fs/ext4/mballoc.c:4458
 ext4_mb_new_blocks+0x5e4/0x4338 fs/ext4/mballoc.c:5765
 ext4_ext_map_blocks+0x1394/0x56f4 fs/ext4/extents.c:4346
 ext4_map_blocks+0x860/0x1778 fs/ext4/inode.c:679
 _ext4_get_block+0x19c/0x4d8 fs/ext4/inode.c:822
 ext4_get_block_unwritten+0x3c/0x110 fs/ext4/inode.c:855
 ext4_block_write_begin+0x50c/0x10e4 fs/ext4/inode.c:1124
 ext4_write_begin+0x5f4/0x131c fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x348/0x990 fs/ext4/inode.c:3000
 generic_perform_write+0x234/0x4f4 mm/filemap.c:3862
 ext4_buffered_write_iter+0x2c4/0x528 fs/ext4/file.c:285
 ext4_file_write_iter+0x18c/0x1574 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3ec/0x7f0 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x174/0x20c fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: d4210000 97dbb0f4 d4210000 97dbb0f2 (d4210000) 
---[ end trace 0000000000000000 ]---

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/11 09:28 linux-6.1.y f2ddafa93a25 86914af9 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan-arm64 kernel BUG in ext4_mb_use_inode_pa
* Struck through repros no longer work on HEAD.