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

[syzbot <syzbot+10a214d962941493d1dd@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    911483b25612 Add linux-next specific files for 20250604
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=161761d4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=28859360c84ac63d
dashboard link: https://syzkaller.appspot.com/bug?extid=10a214d962941493d1dd
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1106940c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10ce7c82580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1067df4a0ae9/disk-911483b2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1ec468cccc74/vmlinux-911483b2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02250b138a0f/bzImage-911483b2.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/ac45824a405f/mount_0.gz

The issue was bisected to:

commit ad7a2ae339342ce4721993e637ecd9f7dc654f3b
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date:   Mon Jun 2 00:22:17 2025 +0000

    bcachefs: Add missing restart handling to check_topology()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=162c2c0c580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=152c2c0c580000
console output: https://syzkaller.appspot.com/x/log.txt?x=112c2c0c580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+10a214d962941493d1dd@syzkaller.appspotmail.com
Fixes: ad7a2ae33934 ("bcachefs: Add missing restart handling to check_topology()")

bcachefs (loop0): error in recovery: ENOMEMemergency read only at seq 10
bcachefs (loop0): bch2_fs_start(): error starting filesystem ENOMEM
bcachefs (loop0): shutting down
bcachefs (loop0): shutdown complete
bcachefs: bch2_fs_get_tree() error: ENOMEM
Filesystem bcachefs get_tree() didn't set fc->root, returned 12
------------[ cut here ]------------
kernel BUG at fs/super.c:1812!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 5842 Comm: syz-executor187 Not tainted 6.15.0-next-20250604-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:vfs_get_tree+0x29f/0x2b0 fs/super.c:1812
Code: 1b 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 14 8b ee ff 48 8b 33 48 c7 c7 00 31 99 8b 44 89 f2 e8 d2 42 f2 fe 90 <0f> 0b 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc9000437fd58 EFLAGS: 00010246
RAX: 000000000000003f RBX: ffffffff8e7829a0 RCX: ad6f5de195933e00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa9ec R12: 1ffff1100ea3c216
R13: dffffc0000000000 R14: 000000000000000c R15: 0000000000000000
FS:  000055558ea4c380(0000) GS:ffff888125c4d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005620027d9f60 CR3: 0000000075234000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_new_mount+0x24a/0xa40 fs/namespace.c:3874
 do_mount fs/namespace.c:4211 [inline]
 __do_sys_mount fs/namespace.c:4422 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4399
 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: 0033:0x7ff57623fe2a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffda26af7f8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffda26af810 RCX: 00007ff57623fe2a
RDX: 00002000000000c0 RSI: 0000200000000000 RDI: 00007ffda26af810
RBP: 0000200000000000 R08: 00007ffda26af850 R09: 0000000000005972
R10: 0000000000800000 R11: 0000000000000282 R12: 00002000000000c0
R13: 00007ffda26af850 R14: 0000000000000003 R15: 0000000000800000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:vfs_get_tree+0x29f/0x2b0 fs/super.c:1812
Code: 1b 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 14 8b ee ff 48 8b 33 48 c7 c7 00 31 99 8b 44 89 f2 e8 d2 42 f2 fe 90 <0f> 0b 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc9000437fd58 EFLAGS: 00010246
RAX: 000000000000003f RBX: ffffffff8e7829a0 RCX: ad6f5de195933e00
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff1bfa9ec R12: 1ffff1100ea3c216
R13: dffffc0000000000 R14: 000000000000000c R15: 0000000000000000
FS:  000055558ea4c380(0000) GS:ffff888125c4d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe40667f19 CR3: 0000000075234000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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