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Message-ID: <197c44ef-aa46-466e-9381-a0edff657762@gmx.com>
Date: Thu, 26 Jun 2025 15:35:40 +0930
From: Qu Wenruo <quwenruo.btrfs@....com>
To: syzbot <syzbot+fa90fcaa28f5cd4b1fc1@...kaller.appspotmail.com>,
clm@...com, dsterba@...e.com, josef@...icpanda.com,
linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com, wqu@...e.com
Subject: Re: [syzbot] [btrfs?] possible deadlock in btrfs_read_chunk_tree
#syz test: https://github.com/adam900710/linux.git shutdown
在 2025/6/24 22:41, syzbot 写道:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 5d4809e25903 Add linux-next specific files for 20250620
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1421b370580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=58afc4b78b52b7e3
> dashboard link: https://syzkaller.appspot.com/bug?extid=fa90fcaa28f5cd4b1fc1
> 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=11f1cb0c580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14aff30c580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/16492bf6b788/disk-5d4809e2.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/7be284ded1de/vmlinux-5d4809e2.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/467d717f0d9c/bzImage-5d4809e2.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/4a74fbfa0b0f/mount_0.gz
> fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=1030cdd4580000)
>
> The issue was bisected to:
>
> commit 7aacdf6feed1ca882339ebd3895a233373b40a1e
> Author: Qu Wenruo <wqu@...e.com>
> Date: Tue Jun 17 05:19:38 2025 +0000
>
> btrfs: delay btrfs_open_devices() until super block is created
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14d29b0c580000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=16d29b0c580000
> console output: https://syzkaller.appspot.com/x/log.txt?x=12d29b0c580000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+fa90fcaa28f5cd4b1fc1@...kaller.appspotmail.com
> Fixes: 7aacdf6feed1 ("btrfs: delay btrfs_open_devices() until super block is created")
>
> BTRFS info (device loop0): using sha256 (sha256-x86_64) checksum algorithm
> BTRFS info (device loop0): disk space caching is enabled
> BTRFS warning (device loop0): space cache v1 is being deprecated and will be removed in a future release, please use -o space_cache=v2
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.16.0-rc2-next-20250620-syzkaller #0 Not tainted
> ------------------------------------------------------
> syz-executor123/5843 is trying to acquire lock:
> ffffffff8e6e9fe8 (uuid_mutex){+.+.}-{4:4}, at: btrfs_read_chunk_tree+0xef/0x2170 fs/btrfs/volumes.c:7462
>
> but task is already holding lock:
> ffff8880328ea0e0 (&type->s_umount_key#41/1){+.+.}-{4:4}, at: alloc_super+0x204/0x970 fs/super.c:345
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (&type->s_umount_key#41/1){+.+.}-{4:4}:
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> down_write_nested+0x9d/0x200 kernel/locking/rwsem.c:1693
> alloc_super+0x204/0x970 fs/super.c:345
> sget_fc+0x329/0xa40 fs/super.c:761
> btrfs_get_tree_super fs/btrfs/super.c:1867 [inline]
> btrfs_get_tree_subvol fs/btrfs/super.c:2059 [inline]
> btrfs_get_tree+0x4c6/0x12d0 fs/btrfs/super.c:2093
> vfs_get_tree+0x8f/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
>
> -> #0 (uuid_mutex){+.+.}-{4:4}:
> check_prev_add kernel/locking/lockdep.c:3168 [inline]
> check_prevs_add kernel/locking/lockdep.c:3287 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> __mutex_lock_common kernel/locking/mutex.c:602 [inline]
> __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
> btrfs_read_chunk_tree+0xef/0x2170 fs/btrfs/volumes.c:7462
> open_ctree+0x17f2/0x3a10 fs/btrfs/disk-io.c:3458
> btrfs_fill_super fs/btrfs/super.c:984 [inline]
> btrfs_get_tree_super fs/btrfs/super.c:1922 [inline]
> btrfs_get_tree_subvol fs/btrfs/super.c:2059 [inline]
> btrfs_get_tree+0xc6f/0x12d0 fs/btrfs/super.c:2093
> vfs_get_tree+0x8f/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
>
> other info that might help us debug this:
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&type->s_umount_key#41/1);
> lock(uuid_mutex);
> lock(&type->s_umount_key#41/1);
> lock(uuid_mutex);
>
> *** DEADLOCK ***
>
> 1 lock held by syz-executor123/5843:
> #0: ffff8880328ea0e0 (&type->s_umount_key#41/1){+.+.}-{4:4}, at: alloc_super+0x204/0x970 fs/super.c:345
>
> stack backtrace:
> CPU: 1 UID: 0 PID: 5843 Comm: syz-executor123 Not tainted 6.16.0-rc2-next-20250620-syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
> check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
> check_prev_add kernel/locking/lockdep.c:3168 [inline]
> check_prevs_add kernel/locking/lockdep.c:3287 [inline]
> validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
> __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
> lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
> __mutex_lock_common kernel/locking/mutex.c:602 [inline]
> __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
> btrfs_read_chunk_tree+0xef/0x2170 fs/btrfs/volumes.c:7462
> open_ctree+0x17f2/0x3a10 fs/btrfs/disk-io.c:3458
> btrfs_fill_super fs/btrfs/super.c:984 [inline]
> btrfs_get_tree_super fs/btrfs/super.c:1922 [inline]
> btrfs_get_tree_subvol fs/btrfs/super.c:2059 [inline]
> btrfs_get_tree+0xc6f/0x12d0 fs/btrfs/super.c:2093
> vfs_get_tree+0x8f/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: 0033:0x7fda63124f3a
> 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:00007ffd76f19cb8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 00007ffd76f19cd0 RCX: 00007fda63124f3a
> RDX: 00002000000004c0 RSI: 00002000000015c0 RDI: 00007ffd76f19cd0
> RBP: 00002000000004c0 R08: 00007ffd76f19d10 R09: 0000000000005598
> R10: 0000000002000000 R11: 0000000000000282 R12: 00002000000015c0
> R13: 00007ffd76f19d10 R14: 0000000000000003 R15: 0000000002000000
> </TASK>
> BTRFS info (device loop0): rebuilding free space tree
> BTRFS info (device loop0): disabling free space tree
> BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE (0x1)
> BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPACE_TREE_VALID (0x2)
>
>
> ---
> 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.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
> 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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