Message-Id: <4B44CAF4-89D2-415B-8D29-13FB7767A1D3@gmail.com>
Date: Thu, 3 Jul 2025 15:19:35 +0800
From: Alan Huang <mmpgouride@...il.com>
To: syzbot <syzbot+8deb6ff4415db67a9f18@...kaller.appspotmail.com>
Cc: kent.overstreet@...ux.dev,
 linux-bcachefs@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bcachefs?] kernel BUG in __btree_trans_update_by_path

On Jul 3, 2025, at 13:15, syzbot <syzbot+8deb6ff4415db67a9f18@...kaller.appspotmail.com> wrote:
> 
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    50c8770a42fa Add linux-next specific files for 20250702
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1191aebc580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d831c9dfe03f77ec
> dashboard link: https://syzkaller.appspot.com/bug?extid=8deb6ff4415db67a9f18
> 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=1311d3d4580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1770f982580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/eb40fda2e0ca/disk-50c8770a.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cba4d214940c/vmlinux-50c8770a.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4b23ed647866/bzImage-50c8770a.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/cd313604f9e1/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8deb6ff4415db67a9f18@...kaller.appspotmail.com
> 
>  while marking u64s 11 type btree_ptr_v2 SPOS_MAX len 0 ver 0: seq 1db8f60c84bb244c written 8 min_key POS_MIN durability: 1 ptr: 0:42:0 gen 0, fixing
> done
> bcachefs (loop0): going read-write
> bcachefs (loop0): journal_replay...
> ------------[ cut here ]------------
> kernel BUG at fs/bcachefs/btree_update.c:339!

Caused by commit b47a82ff4772ea9d7091b85ef5f34dc78c866a02 (“bcachefs: Only run 'increase_depth' for keys from btree node csan”)

The commit add an additional condition: !k->allocated


> Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
> CPU: 0 UID: 0 PID: 5842 Comm: syz-executor286 Not tainted 6.16.0-rc4-next-20250702-syzkaller #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
> RIP: 0010:__btree_trans_update_by_path+0x1fd3/0x2010 fs/bcachefs/btree_update.c:339
> Code: f6 ff ff 48 8b 7c 24 28 e8 ca dd f5 fd 48 ba 00 00 00 00 00 fc ff df e9 3d f6 ff ff e8 a6 c9 91 fd 90 0f 0b e8 9e c9 91 fd 90 <0f> 0b e8 96 c9 91 fd 90 0f 0b e8 8e c9 91 fd 90 0f 0b e8 86 c9 91
> RSP: 0018:ffffc9000413ea18 EFLAGS: 00010293
> RAX: ffffffff842e0b42 RBX: 0000000000008542 RCX: ffff88802ea71e00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff888031194010 R08: ffffffff84518baa R09: 0000000000000002
> R10: 0000000000000003 R11: 0000000000000000 R12: ffff888074e00000
> R13: ffff888031194000 R14: 0000000000000088 R15: 1ffff11006232802
> FS:  000055555e045380(0000) GS:ffff888125c1d000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055e03c677168 CR3: 0000000078920000 CR4: 00000000003526f0
> Call Trace:
> <TASK>
> bch2_trans_update_by_path fs/bcachefs/btree_update.c:454 [inline]
> bch2_trans_update_ip+0x8f6/0x1f00 fs/bcachefs/btree_update.c:546
> bch2_trans_update fs/bcachefs/btree_update.h:123 [inline]
> bch2_journal_replay_key+0x4c1/0xb50 fs/bcachefs/recovery.c:311
> bch2_journal_replay+0x171d/0x2630 fs/bcachefs/recovery.c:396
> bch2_run_recovery_pass fs/bcachefs/recovery_passes.c:484 [inline]
> __bch2_run_recovery_passes+0x392/0x1010 fs/bcachefs/recovery_passes.c:539
> bch2_run_recovery_passes+0x184/0x210 fs/bcachefs/recovery_passes.c:610
> bch2_fs_recovery+0x2690/0x3a50 fs/bcachefs/recovery.c:1005
> bch2_fs_start+0xaaf/0xda0 fs/bcachefs/super.c:1212
> bch2_fs_get_tree+0xb39/0x1540 fs/bcachefs/fs.c:2488
> vfs_get_tree+0x92/0x2b0 fs/super.c:1804
> do_new_mount+0x24a/0xa40 fs/namespace.c:3902
> do_mount fs/namespace.c:4239 [inline]
> __do_sys_mount fs/namespace.c:4450 [inline]
> __se_sys_mount+0x317/0x410 fs/namespace.c:4427
> 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: 0033:0x7f878cb709ba
> 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:00007ffc9f662588 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 00007ffc9f6625a0 RCX: 00007f878cb709ba
> RDX: 00002000000000c0 RSI: 0000200000000080 RDI: 00007ffc9f6625a0
> RBP: 0000200000000080 R08: 00007ffc9f6625e0 R09: 00000000000059b9
> R10: 0000000000818001 R11: 0000000000000282 R12: 00002000000000c0
> R13: 0000000000000004 R14: 0000000000000003 R15: 00007ffc9f6625e0
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__btree_trans_update_by_path+0x1fd3/0x2010 fs/bcachefs/btree_update.c:339
> Code: f6 ff ff 48 8b 7c 24 28 e8 ca dd f5 fd 48 ba 00 00 00 00 00 fc ff df e9 3d f6 ff ff e8 a6 c9 91 fd 90 0f 0b e8 9e c9 91 fd 90 <0f> 0b e8 96 c9 91 fd 90 0f 0b e8 8e c9 91 fd 90 0f 0b e8 86 c9 91
> RSP: 0018:ffffc9000413ea18 EFLAGS: 00010293
> RAX: ffffffff842e0b42 RBX: 0000000000008542 RCX: ffff88802ea71e00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff888031194010 R08: ffffffff84518baa R09: 0000000000000002
> R10: 0000000000000003 R11: 0000000000000000 R12: ffff888074e00000
> R13: ffff888031194000 R14: 0000000000000088 R15: 1ffff11006232802
> FS:  000055555e045380(0000) GS:ffff888125d1d000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f8f8b3a1796 CR3: 0000000078920000 CR4: 00000000003526f0
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup
> 

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