[syzbot] [bcachefs?] kernel BUG in bch2_fs_free (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fec734e8d564 Merge tag 'riscv-for-linus-v6.17-rc8' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14df3142580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4d8792ecb6308d0f
dashboard link: https://syzkaller.appspot.com/bug?extid=f2fb0a1f147a67cd3ac1
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c50776ae92ae/disk-fec734e8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b1489b275504/vmlinux-fec734e8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4b4c062dc0ea/bzImage-fec734e8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f2fb0a...@syzkaller.appspotmail.com

bcachefs (loop0): error in recovery: EINTR
emergency read only at seq 11
bcachefs (loop0): bch2_fs_start(): error starting filesystem EINTR
bcachefs (loop0): shutting down
------------[ cut here ]------------
kernel BUG at fs/bcachefs/super.c:725!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 4520 Comm: syz.0.7943 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:bch2_fs_free+0x59c/0x5a0 fs/bcachefs/super.c:725
Code: e8 f9 d4 c9 fd e9 16 fc ff ff 89 d9 80 e1 07 38 c1 0f 8c 72 ff ff ff 48 89 df e8 df d4 c9 fd e9 65 ff ff ff e8 d5 57 66 fd 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41
RSP: 0018:ffffc90004b7f918 EFLAGS: 00010246
RAX: ffffffff8459631b RBX: 0000000000000002 RCX: 0000000000080000
RDX: ffffc9000c0d1000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffff888056a36000 R08: ffff888056a36047 R09: 1ffff1100ad46c08
R10: dffffc0000000000 R11: ffffed100ad46c09 R12: 1ffff11013ec00f0
R13: 0000000000000000 R14: ffffffff8e7a84a0 R15: ffff88809f600782
FS: 00007f88c92746c0(0000) GS:ffff888125c12000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000057030 CR3: 0000000061ea0000 CR4: 0000000000350ef0
Call Trace:
<TASK>
bch2_fs_get_tree+0xb6e/0x1520 fs/bcachefs/fs.c:2604
vfs_get_tree+0x92/0x2b0 fs/super.c:1815
do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808
do_mount fs/namespace.c:4136 [inline]
__do_sys_mount fs/namespace.c:4347 [inline]
__se_sys_mount+0x317/0x410 fs/namespace.c:4324
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: 0033:0x7f88c839066a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007f88c9273e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f88c9273ef0 RCX: 00007f88c839066a
RDX: 0000200000000200 RSI: 0000200000000000 RDI: 00007f88c9273eb0
RBP: 0000200000000200 R08: 00007f88c9273ef0 R09: 0000000001800402
R10: 0000000001800402 R11: 0000000000000246 R12: 0000200000000000
R13: 00007f88c9273eb0 R14: 0000000000005962 R15: 0000200000000540
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:bch2_fs_free+0x59c/0x5a0 fs/bcachefs/super.c:725
Code: e8 f9 d4 c9 fd e9 16 fc ff ff 89 d9 80 e1 07 38 c1 0f 8c 72 ff ff ff 48 89 df e8 df d4 c9 fd e9 65 ff ff ff e8 d5 57 66 fd 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41
RSP: 0018:ffffc90004b7f918 EFLAGS: 00010246
RAX: ffffffff8459631b RBX: 0000000000000002 RCX: 0000000000080000
RDX: ffffc9000c0d1000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffff888056a36000 R08: ffff888056a36047 R09: 1ffff1100ad46c08
R10: dffffc0000000000 R11: ffffed100ad46c09 R12: 1ffff11013ec00f0
R13: 0000000000000000 R14: ffffffff8e7a84a0 R15: ffff88809f600782
FS: 00007f88c92746c0(0000) GS:ffff888125c12000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000057030 CR3: 0000000061ea0000 CR4: 0000000000350ef0


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