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AJvYcCWAtZfiu2sdhhWKmJ2iHlohVaF+h8RDHDvamoELh1+YZbNw+0tTuONZSYcBrB1cvRWwHhz/0yj0W5UIPP4U@vger.kernel.org X-Gm-Message-State: AOJu0YzgUU3DBnVKHqsjpxjnOqp37jCMNS96W9V0ltYO7TdK876GYpz4 7pgQpN698T+aVxxjDzGDbx1RV0etVYLEKyak2j0dvToJbsI0uOPGEB8VNt4Cui3VffJZthizERC 1P/l3qg3V2CmbfMKmfudnQ8yw/j65vvDmSt33H66XvkpPGCOj6PiJ9K3QTYU= Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:1694:b0:65f:64fa:172e with SMTP id 006d021491bc7-661006e73demr3578307eaf.57.1768470624723; Thu, 15 Jan 2026 01:50:24 -0800 (PST) Date: Thu, 15 Jan 2026 01:50:24 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6968b860.050a0220.58bed.0018.GAE@google.com> Subject: [syzbot] [fs?] possible deadlock in put_mnt_ns From: syzbot To: brauner@kernel.org, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 0f853ca2a798 Add linux-next specific files for 20260113 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1386f99a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=789b351b8a4cafe1 dashboard link: https://syzkaller.appspot.com/bug?extid=55fd613012e606d75d45 compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1482859a580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13402052580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/9c7778b6d6be/disk-0f853ca2.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/ea278b0d6aff/vmlinux-0f853ca2.xz kernel image: https://storage.googleapis.com/syzbot-assets/60b94236c918/bzImage-0f853ca2.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+55fd613012e606d75d45@syzkaller.appspotmail.com R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fca229e5fa0 R14: 00007fca229e5fa0 R15: 0000000000000003 ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.0.23/6026 is trying to acquire lock: ffffffff8e49efd0 (namespace_sem){++++}-{4:4}, at: namespace_lock fs/namespace.c:1730 [inline] ffffffff8e49efd0 (namespace_sem){++++}-{4:4}, at: class_namespace_excl_constructor fs/namespace.c:101 [inline] ffffffff8e49efd0 (namespace_sem){++++}-{4:4}, at: put_mnt_ns+0x170/0x2f0 fs/namespace.c:6241 but task is already holding lock: ffffffff8e49efd0 (namespace_sem){++++}-{4:4}, at: namespace_lock fs/namespace.c:1730 [inline] ffffffff8e49efd0 (namespace_sem){++++}-{4:4}, at: lock_mount_exact+0x89/0x630 fs/namespace.c:3852 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(namespace_sem); lock(namespace_sem); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by syz.0.23/6026: #0: ffff888149040148 (&sb->s_type->i_mutex_key){++++}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline] #0: ffff888149040148 (&sb->s_type->i_mutex_key){++++}-{4:4}, at: lock_mount_exact+0x7d/0x630 fs/namespace.c:3851 #1: ffffffff8e49efd0 (namespace_sem){++++}-{4:4}, at: namespace_lock fs/namespace.c:1730 [inline] #1: ffffffff8e49efd0 (namespace_sem){++++}-{4:4}, at: lock_mount_exact+0x89/0x630 fs/namespace.c:3852 stack backtrace: CPU: 1 UID: 0 PID: 6026 Comm: syz.0.23 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain kernel/locking/lockdep.c:3895 [inline] __lock_acquire+0x2540/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868 down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590 namespace_lock fs/namespace.c:1730 [inline] class_namespace_excl_constructor fs/namespace.c:101 [inline] put_mnt_ns+0x170/0x2f0 fs/namespace.c:6241 prepare_anon_dentry fs/libfs.c:2167 [inline] path_from_stashed+0x40a/0x5c0 fs/libfs.c:2252 open_namespace_file+0x8f/0x130 fs/nsfs.c:108 open_new_namespace fs/namespace.c:3174 [inline] vfs_open_tree+0xa9d/0xf50 fs/namespace.c:3220 __do_sys_open_tree fs/namespace.c:3230 [inline] __se_sys_open_tree fs/namespace.c:3228 [inline] __x64_sys_open_tree+0x96/0x110 fs/namespace.c:3228 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fca2278f749 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:00007ffc7a04e728 EFLAGS: 00000246 ORIG_RAX: 00000000000001ac RAX: ffffffffffffffda RBX: 00007fca229e5fa0 RCX: 00007fca2278f749 RDX: 0000000000001802 RSI: 0000200000000000 RDI: ffffffffffffffff RBP: 00007ffc7a04e780 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fca229e5fa0 R14: 00007fca229e5fa0 R15: 0000000000000003 --- 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@googlegroups.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