WARNING in btrfs_add_to_free_space_tree (2)

Status: upstream: reported on 2026/08/23 05:23
Subsystems: btrfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+554a2e08e4abc56984a9@syzkaller.appspotmail.com
First crash: 5d20h, last: 3d10h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
4d946bbf assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in btrfs_add_to_free_space_tree (2) 2026/08/21 01:00 2026/08/21 01:00 2026/08/21 01:44 1e72964b
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [btrfs?] WARNING in btrfs_add_to_free_space_tree (2) 0 (1) 2026/08/23 05:23
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in btrfs_add_to_free_space_tree btrfs -1 1 264d 260d 0/29 auto-obsoleted due to no activity on 2026/03/13 05:08

Sample crash report:
loop0: detected capacity change from 0 to 32768
BTRFS: device fsid 395ef67a-297e-477c-816d-cd80a5b93e5d devid 1 transid 8 /dev/loop0 (7:0) scanned by syz.0.0 (5311)
BTRFS info (device loop0): first mount of filesystem 395ef67a-297e-477c-816d-cd80a5b93e5d
BTRFS info (device loop0): using sha256 checksum algorithm
BTRFS info (device loop0): rebuilding free space tree
BTRFS info (device loop0): enabling ssd optimizations
BTRFS info (device loop0): using spread ssd allocation scheme
BTRFS info (device loop0): turning on async discard
BTRFS info (device loop0): enabling free space tree
BTRFS info (device loop0): force clearing of disk cache
loop0: detected capacity change from 32768 to 32767
------------[ cut here ]------------
btrfs_abort_should_print_stack(__error)
WARNING: fs/btrfs/free-space-tree.c:1050 at btrfs_add_to_free_space_tree+0x4e1/0x5b0 fs/btrfs/free-space-tree.c:1050, CPU#0: syz.0.0/5311
Modules linked in:
CPU: 0 UID: 0 PID: 5311 Comm: syz.0.0 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
RIP: 0010:btrfs_add_to_free_space_tree+0x4e1/0x5b0 fs/btrfs/free-space-tree.c:1050
Code: e2 74 1a 41 83 fd fb 74 0d 41 83 fd f4 75 15 e8 65 ba 8c fd eb 17 e8 5e ba 8c fd eb 10 e8 57 ba 8c fd eb 09 e8 50 ba 8c fd 90 <0f> 0b 90 44 89 e9 f7 d9 4c 8b 24 24 e9 95 fe ff ff 89 d9 80 e1 07
RSP: 0018:ffffc9000f29f3f0 EFLAGS: 00010287
RAX: ffffffff843a7a70 RBX: ffff888051a74001 RCX: 0000000000100000
RDX: ffffc9000e901000 RSI: 00000000000038d7 RDI: 00000000000038d8
RBP: ffff88801276a5e0 R08: ffff88801f99cb00 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000002 R12: ffff8880138e2db8
R13: 00000000ffffffe4 R14: ffff88801fc77630 R15: 1ffff110024ed4c8
FS:  00007f00ab5f36c0(0000) GS:ffff88808c30a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f00ab5b0fe8 CR3: 0000000043b27000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 do_free_extent_accounting fs/btrfs/extent-tree.c:3191 [inline]
 __btrfs_free_extent+0x1461/0x39c0 fs/btrfs/extent-tree.c:3558
 run_delayed_tree_ref fs/btrfs/extent-tree.c:1824 [inline]
 run_one_delayed_ref fs/btrfs/extent-tree.c:1851 [inline]
 btrfs_run_delayed_refs_for_head fs/btrfs/extent-tree.c:2058 [inline]
 __btrfs_run_delayed_refs+0x166c/0x43b0 fs/btrfs/extent-tree.c:2134
 btrfs_run_delayed_refs+0xdc/0x2a0 fs/btrfs/extent-tree.c:2246
 btrfs_commit_transaction+0x28a/0x30b0 fs/btrfs/transaction.c:2256
 btrfs_quota_enable+0x10ff/0x1e20 fs/btrfs/qgroup.c:1237
 btrfs_ioctl_quota_ctl+0x186/0x1f0 fs/btrfs/ioctl.c:3566
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f00aa79e0d9
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:00007f00ab5f2fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f00aaa25fa0 RCX: 00007f00aa79e0d9
RDX: 00002000000000c0 RSI: 00000000c0109428 RDI: 0000000000000003
RBP: 00007f00aa835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f00aaa26038 R14: 00007f00aaa25fa0 R15: 00007ffd0ce801f8
 </TASK>

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/21 15:39 upstream 818bebeb63dd 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 22:45 upstream bd5f485f3f02 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 21:37 upstream bd5f485f3f02 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 17:56 upstream bd5f485f3f02 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 05:17 upstream b126f6f5940f 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
2026/08/19 05:16 upstream b126f6f5940f 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in btrfs_add_to_free_space_tree
* Struck through repros no longer work on HEAD.