WARNING in __add_block_group_free_space

Status: upstream: reported on 2026/08/10 00:34
Subsystems: btrfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+6931616d57696102d8aa@syzkaller.appspotmail.com
First crash: 21d, last: now
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ID Workflow Result Correct Bug Created Started Finished Revision
e6217e5c assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ❌ ❓ WARNING in __add_block_group_free_space 2026/08/09 12:56 2026/08/09 12:56 2026/08/09 13:30 5d63f80b
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[syzbot] [btrfs?] WARNING in __add_block_group_free_space 0 (1) 2026/08/10 00:34

Sample crash report:
------------[ cut here ]------------
btrfs_abort_should_print_stack(__error)
WARNING: fs/btrfs/free-space-tree.c:1440 at __add_block_group_free_space+0x5a3/0x5b0 fs/btrfs/free-space-tree.c:1440, CPU#0: kworker/u4:6/177
Modules linked in:
CPU: 0 UID: 0 PID: 177 Comm: kworker/u4:6 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound btrfs_async_reclaim_metadata_space
RIP: 0010:__add_block_group_free_space+0x5a3/0x5b0 fs/btrfs/free-space-tree.c:1440
Code: 07 38 c1 0f 8c ce fc ff ff 4c 89 f7 e8 56 dd fd fd e9 c1 fc ff ff e8 8c 94 8c fd eb 10 e8 85 94 8c fd eb 09 e8 7e 94 8c fd 90 <0f> 0b 90 44 89 e1 f7 d9 e9 51 fe ff ff 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900017f7498 EFLAGS: 00010293
RAX: ffffffff843aa042 RBX: ffff888051b64001 RCX: ffff8880334e4b00
RDX: 0000000000000000 RSI: ffffffff8f3fff60 RDI: 00000000ffffffe4
RBP: ffff88801fcbbd60 R08: ffff8880334e4b00 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000000 R12: 00000000ffffffe4
R13: ffff8880127e9630 R14: ffff88801fcbbdc0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88808c30a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdfa30b5210 CR3: 000000001223c000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 btrfs_add_block_group_free_space+0xd0/0x130 fs/btrfs/free-space-tree.c:1465
 btrfs_create_pending_block_groups+0xcc6/0x15e0 fs/btrfs/block-group.c:2957
 __btrfs_end_transaction+0x140/0x640 fs/btrfs/transaction.c:1090
 flush_space+0x3e9/0xde0 fs/btrfs/space-info.c:912
 do_async_reclaim_metadata_space+0x3e8/0x940 fs/btrfs/space-info.c:1211
 btrfs_async_reclaim_metadata_space+0x89/0xe0 fs/btrfs/space-info.c:1278
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/26 12:36 upstream 818bebeb63dd a2b77b9e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/26 10:20 upstream 818bebeb63dd 6a91adb4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/25 20:02 upstream 818bebeb63dd a9a1fc32 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/25 15:26 upstream 818bebeb63dd a9a1fc32 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/23 07:44 upstream 818bebeb63dd 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/17 19:31 upstream 8d3ae59288f1 905244d6 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/12 06:57 upstream f5bbbfec59b4 f8d35649 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/10 02:54 upstream b643e495ae92 5d63f80b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/09 06:17 upstream 06cf61899d64 5d63f80b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/08 14:24 upstream a59f57e2aa12 5d63f80b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/07 15:13 upstream f9a2394a2348 e4ef95d6 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/05 07:49 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/05 07:37 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
2026/08/04 18:02 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in __add_block_group_free_space
* Struck through repros no longer work on HEAD.