linux-kernel - [syzbot] [btrfs?] WARNING in btrfs_lookup_extent

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Message-ID: <688d0dde.050a0220.f0410.0130.GAE@google.com>
Date: Fri, 01 Aug 2025 11:56:30 -0700
From: syzbot <syzbot+c035bce0effd1de39e05@...kaller.appspotmail.com>
To: clm@...com, dsterba@...e.com, josef@...icpanda.com, 
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [btrfs?] WARNING in btrfs_lookup_extent_info (2)

Hello,

syzbot found the following issue on:

HEAD commit:    038d61fd6422 Linux 6.16
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17bd14a2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=831eea247244ce8c
dashboard link: https://syzkaller.appspot.com/bug?extid=c035bce0effd1de39e05
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-038d61fd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/45453fb53a5d/vmlinux-038d61fd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4094774b8a7e/bzImage-038d61fd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c035bce0effd1de39e05@...kaller.appspotmail.com

BTRFS info (device loop0): balance: start -d -m
BTRFS info (device loop0): relocating block group 6881280 flags data|metadata
BTRFS info (device loop0): relocating block group 5242880 flags data|metadata
------------[ cut here ]------------
WARNING: CPU: 0 PID: 5337 at fs/btrfs/extent-tree.c:209 btrfs_lookup_extent_info+0xcc6/0xd80 fs/btrfs/extent-tree.c:209
Modules linked in:
CPU: 0 UID: 0 PID: 5337 Comm: syz.0.0 Not tainted 6.16.0-syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:btrfs_lookup_extent_info+0xcc6/0xd80 fs/btrfs/extent-tree.c:209
Code: 8b ff ff ff 48 8b 7c 24 50 48 c7 c6 31 97 ae 8d ba a9 00 00 00 b9 8b ff ff ff e8 c5 85 6a fd e9 16 fe ff ff e8 0b ee 00 fe 90 <0f> 0b 90 e9 6d fd ff ff e8 dd 44 b0 07 89 d9 80 e1 07 38 c1 0f 8c
RSP: 0018:ffffc9000ddfeea0 EFLAGS: 00010293
RAX: ffffffff83bf4305 RBX: ffff8880363d43b0 RCX: ffff8880118c0000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000ddff000 R08: ffff8880363d43b3 R09: 1ffff11006c7a876
R10: dffffc0000000000 R11: ffffed1006c7a877 R12: dffffc0000000000
R13: ffff88805325c6d4 R14: 0000000000000000 R15: ffffc9000ddff0c0
FS:  00007fe87d3d46c0(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000453000 CR3: 0000000011d7e000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 update_ref_for_cow+0x998/0x1210 fs/btrfs/ctree.c:373
 btrfs_force_cow_block+0x9d4/0x1e10 fs/btrfs/ctree.c:527
 btrfs_cow_block+0x40a/0x830 fs/btrfs/ctree.c:688
 do_relocation+0xd64/0x1610 fs/btrfs/relocation.c:2275
 relocate_tree_block fs/btrfs/relocation.c:2528 [inline]
 relocate_tree_blocks+0x118b/0x1e90 fs/btrfs/relocation.c:2635
 relocate_block_group+0x760/0xd90 fs/btrfs/relocation.c:3607
 btrfs_relocate_block_group+0x966/0xde0 fs/btrfs/relocation.c:4008
 btrfs_relocate_chunk+0x12a/0x3b0 fs/btrfs/volumes.c:3437
 __btrfs_balance+0x1870/0x21d0 fs/btrfs/volumes.c:4212
 btrfs_balance+0xc94/0x11d0 fs/btrfs/volumes.c:4589
 btrfs_ioctl_balance+0x3d3/0x610 fs/btrfs/ioctl.c:3583
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe880f8e9a9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe87d3d4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe8811b6080 RCX: 00007fe880f8e9a9
RDX: 0000200000000180 RSI: 00000000c4009420 RDI: 0000000000000005
RBP: 00007fe881010d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fe8811b6080 R15: 00007ffc53dc1948
 </TASK>


---
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