syzbot


WARNING in create_reloc_root

Status: upstream: reported on 2026/07/09 08:51
Subsystems: btrfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+aca623fc25065fa06615@syzkaller.appspotmail.com
First crash: 6d08h, last: 6d08h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
13798e9d-2961-4fac-974c-96a83c762f0c assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in create_reloc_root 2026/07/07 00:05 2026/07/07 00:05 2026/07/07 01:15 93f579545ae410f5bccfa141d2e7bf03178f036c

			
		
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[syzbot] [btrfs?] WARNING in create_reloc_root 0 (1) 2026/07/09 08:51

Sample crash report:
FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 1
CPU: 0 UID: 0 PID: 5321 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
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 fail_dump lib/fault-inject.c:73 [inline]
 should_fail_ex+0x40c/0x560 lib/fault-inject.c:174
 should_failslab+0xa8/0x100 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4567 [inline]
 slab_alloc_node mm/slub.c:4925 [inline]
 __kmalloc_cache_noprof+0xa8/0x660 mm/slub.c:5511
 _kmalloc_noprof include/linux/slab.h:969 [inline]
 __add_reloc_root+0x75/0x4e0 fs/btrfs/relocation.c:577
 btrfs_init_reloc_root+0x3d6/0x590 fs/btrfs/relocation.c:800
 record_root_in_trans+0x27c/0x330 fs/btrfs/transaction.c:462
 btrfs_record_root_in_trans+0x15a/0x180 fs/btrfs/transaction.c:508
 start_transaction+0x3a6/0x18b0 fs/btrfs/transaction.c:794
 create_snapshot fs/btrfs/ioctl.c:795 [inline]
 btrfs_mksubvol+0x8c6/0x10c0 fs/btrfs/ioctl.c:887
 btrfs_mksnapshot+0xa3/0xe0 fs/btrfs/ioctl.c:929
 __btrfs_ioctl_snap_create+0x45d/0x6b0 fs/btrfs/ioctl.c:1191
 btrfs_ioctl_snap_create_v2+0x1e9/0x370 fs/btrfs/ioctl.c:1261
 btrfs_ioctl+0x8eb/0xd50 fs/btrfs/ioctl.c:-1
 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:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc6fe59de59
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:00007fc6ff51bfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc6fe826090 RCX: 00007fc6fe59de59
RDX: 0000200000002480 RSI: 0000000050009417 RDI: 0000000000000005
RBP: 00007fc6ff51c050 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007fc6fe826128 R14: 00007fc6fe826090 R15: 00007ffc03132988
 </TASK>
------------[ cut here ]------------
btrfs_abort_should_print_stack(__error)
WARNING: fs/btrfs/relocation.c:735 at create_reloc_root+0x9d2/0xb80 fs/btrfs/relocation.c:735, CPU#0: syz.0.0/5321
Modules linked in:
CPU: 0 UID: 0 PID: 5321 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:create_reloc_root+0x9d2/0xb80 fs/btrfs/relocation.c:735
Code: 25 10 f8 f8 43 c6 44 25 12 f8 49 c7 c7 8b ff ff ff e9 69 fd ff ff e8 0d e2 9e fd eb 10 e8 06 e2 9e fd eb 09 e8 ff e1 9e fd 90 <0f> 0b 90 44 89 f9 f7 d9 49 bc 00 00 00 00 00 fc ff df e9 36 fe ff
RSP: 0018:ffffc900058575e0 EFLAGS: 00010293
RAX: ffffffff8427a091 RBX: ffff888052cd0001 RCX: ffff88801aeaca80
RDX: 0000000000000000 RSI: ffffffff8f1e83a0 RDI: 00000000ffffffef
RBP: ffffc90005857740 R08: ffff88801aeaca80 R09: 0000000000000003
R10: 00000000fffffffb R11: 0000000000000000 R12: dffffc0000000000
R13: 1ffff92000b0aec4 R14: ffff888043f5b378 R15: 00000000ffffffef
FS:  00007fc6ff51c6c0(0000) GS:ffff88808c54e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000003000 CR3: 0000000042b25000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 btrfs_init_reloc_root+0x2f0/0x590 fs/btrfs/relocation.c:792
 record_root_in_trans+0x27c/0x330 fs/btrfs/transaction.c:462
 btrfs_record_root_in_trans+0x15a/0x180 fs/btrfs/transaction.c:508
 start_transaction+0x3a6/0x18b0 fs/btrfs/transaction.c:794
 btrfs_create_common+0x15c/0x310 fs/btrfs/inode.c:6797
 lookup_open fs/namei.c:4508 [inline]
 open_last_lookups fs/namei.c:4608 [inline]
 path_openat+0x133a/0x3830 fs/namei.c:4860
 do_file_open+0x23e/0x4a0 fs/namei.c:4892
 do_sys_openat2+0x115/0x200 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_openat fs/open.c:1390 [inline]
 __se_sys_openat fs/open.c:1385 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1385
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc6fe59de59
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:00007fc6ff51bfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fc6fe826090 RCX: 00007fc6fe59de59
RDX: 000000000000275a RSI: 0000200000000200 RDI: ffffffffffffff9c
RBP: 00007fc6fe633e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc6fe826128 R14: 00007fc6fe826090 R15: 00007ffc03132988
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/05 08:41 upstream 7404ce516372 fcece630 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in create_reloc_root
* Struck through repros no longer work on HEAD.