From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f78.google.com (mail-oa1-f78.google.com [209.85.160.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8BDD25477E for ; Fri, 14 Aug 2026 00:14:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.78 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786666471; cv=none; b=s2j1hHrTv6NTvlz3ErIqGwjGr37Yu+FUr/CdrpfwEtGddmSYH54k0SmHOdRk11VR2CfmwEATNxrBQilUetdtM2QXCNzLH2P7NE2DowmavXu8h0ZpGRCLZLfuzaJpgA/k8z04xTfsZyLoCv8yTZHysi5OYNSWdGoW+hL5q410Atw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786666471; c=relaxed/simple; bh=9qr9IE8c2P2jq+z162fx57XJxi0xfWCZ27IGJg5JZmI=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=Cj1M4J20SSa2UVnlrkAtvLm8GePNn2OVOlAbNkzuTCN+tFzDAI2jK2pySJB7TsJWRG1O2URgsVdR0CXVHr33Dbfs+QEB0OTGcnMkmjL4FTbpM1fPo+eoICCs76b5hW87H++gm6aSyWtodRzmx/xjx81WcgoWTgla7GTVwlKR9WY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.160.78 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oa1-f78.google.com with SMTP id 586e51a60fabf-456b5122c7cso2132100fac.1 for ; Thu, 13 Aug 2026 17:14:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786666468; x=1787271268; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=Ja7SjhEzE+n5djMzigJ+mZ037NujOfkeHtoAmnylPUk=; b=le+3t1KCcYTMLxgYJEhJIujCxDTcbFVXijdUT0aouLYPhJShjfMXWB+qSUU+to/JNd mbpBhc/6nWCf4kj1MS2i7pCd8o2BTnj1Hhp1a6qKQ6BgU/nYSu328SaPDTFkH/0gCA5X dk4qeiDUhf26QjNmqIbWVz07709kTV3S6QL230Nfe+KAczLoBGiYaGrmirSC2XdqFvlH UMAkZnC5C5agEvRigbgn8oCyeGrMF7jKp25u4+VMQyLYgdZYWztGKkVmoc4IeQlVka4R LIxrtWzui5A1R/5wsPLg3YsbqsBMAGWCHuIOZCCGzeWbFxUH+0Oz7g/cHGr3EozzYI3X 95fw== X-Forwarded-Encrypted: i=1; AHgh+RoINL5P/NGbfurB8LQ/O69bR6ZMYodAn1y+lzitCUAFfOWK9G+4JdxgxPA894+woOonlk+4sJP+IZxlemA=@vger.kernel.org X-Gm-Message-State: AOJu0Yy9Jn17oiC6J8QJAjL85av4EzWaYDXnOzpfr3tNaUeG1gnuYNYu sgCqF1bKVsBsILUMDgcZ7OE+0axbCsJJUEXhn2iOzubVmGZD7zv1JsJZ2LA0YUMs7fc6dpASAg6 Y5CIhjhNJaLY4/cd7Exv43oveVQYRo7sH01PFo0IxLkzhGzGKl3PX3FCLgzA= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:1996:b0:496:9ee:e538 with SMTP id 5614622812f47-4b228008b82mr7675111b6e.5.1786666468499; Thu, 13 Aug 2026 17:14:28 -0700 (PDT) Date: Thu, 13 Aug 2026 17:14:28 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a7e5de4.0d56fcf3.329e18.024b.GAE@google.com> Subject: [syzbot] [block?] possible deadlock in loop_configure From: syzbot To: axboe@kernel.dk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 6b8c8af514d7 Add linux-next specific files for 20260807 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=10b61132580000 kernel config: https://syzkaller.appspot.com/x/.config?x=6d343b54cc50df0f dashboard link: https://syzkaller.appspot.com/bug?extid=a201cc2f7513691d4ed0 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/71ff4edcb608/disk-6b8c8af5.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/1f5fa331d8f2/vmlinux-6b8c8af5.xz kernel image: https://storage.googleapis.com/syzbot-assets/f993558ec63b/bzImage-6b8c8af5.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+a201cc2f7513691d4ed0@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.7.1110/11577 is trying to acquire lock: ffffffff8ec88b00 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:314 [inline] ffffffff8ec88b00 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4636 [inline] ffffffff8ec88b00 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4974 [inline] ffffffff8ec88b00 (fs_reclaim){+.+.}-{0:0}, at: __do_kmalloc_node mm/slub.c:5413 [inline] ffffffff8ec88b00 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_noprof+0xbc/0x710 mm/slub.c:5439 but task is already holding lock: ffff888025c00fe8 (&q->limits_lock){+.+.}-{4:4}, at: queue_limits_start_update include/linux/blkdev.h:1101 [inline] ffff888025c00fe8 (&q->limits_lock){+.+.}-{4:4}, at: loop_configure+0x787/0xdc0 drivers/block/loop.c:1083 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->limits_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 queue_limits_start_update include/linux/blkdev.h:1101 [inline] loop_set_dio drivers/block/loop.c:1460 [inline] lo_simple_ioctl drivers/block/loop.c:1528 [inline] lo_ioctl+0x16ca/0x2150 drivers/block/loop.c:1594 blkdev_ioctl+0x5e3/0x740 block/ioctl.c:798 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x510 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&q->q_usage_counter(io)#26){++++}-{0:0}: blk_alloc_queue+0x544/0x690 block/blk-core.c:504 blk_mq_alloc_queue block/blk-mq.c:4420 [inline] __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4467 loop_add+0x480/0xb40 drivers/block/loop.c:2071 loop_init+0xd7/0x160 drivers/block/loop.c:2310 do_one_initcall+0x250/0x870 init/main.c:1359 do_initcall_level+0x10a/0x1a0 init/main.c:1421 do_initcalls+0x59/0xa0 init/main.c:1437 kernel_init_freeable+0x29d/0x3e0 init/main.c:1672 kernel_init+0x22/0x1d0 init/main.c:1562 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (fs_reclaim){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x15ff/0x2e50 kernel/locking/lockdep.c:5254 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5908 __fs_reclaim_acquire mm/page_alloc.c:4433 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4447 might_alloc include/linux/sched/mm.h:314 [inline] slab_pre_alloc_hook mm/slub.c:4636 [inline] slab_alloc_node mm/slub.c:4974 [inline] __do_kmalloc_node mm/slub.c:5413 [inline] __kmalloc_noprof+0xbc/0x710 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] btrfs_calc_avail_data_space fs/btrfs/super.c:1631 [inline] btrfs_statfs+0xc2a/0x1b40 fs/btrfs/super.c:1781 statfs_by_dentry fs/statfs.c:66 [inline] vfs_statfs+0x147/0x2d0 fs/statfs.c:90 loop_get_discard_config drivers/block/loop.c:774 [inline] loop_update_limits+0x375/0x920 drivers/block/loop.c:984 loop_configure+0x7d2/0xdc0 drivers/block/loop.c:1084 lo_ioctl+0xad5/0x2150 drivers/block/loop.c:1564 blkdev_ioctl+0x5e3/0x740 block/ioctl.c:798 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x510 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: fs_reclaim --> &q->q_usage_counter(io)#26 --> &q->limits_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->limits_lock); lock(&q->q_usage_counter(io)#26); lock(&q->limits_lock); lock(fs_reclaim); *** DEADLOCK *** locks held by syz.7.1110/11577: 2, last CPU#0: #0: ffff888025eba430 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:119 [inline] #0: ffff888025eba430 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_configure+0x35d/0xdc0 drivers/block/loop.c:1038 #1: ffff888025c00fe8 (&q->limits_lock){+.+.}-{4:4}, at: queue_limits_start_update include/linux/blkdev.h:1101 [inline] #1: ffff888025c00fe8 (&q->limits_lock){+.+.}-{4:4}, at: loop_configure+0x787/0xdc0 drivers/block/loop.c:1083 stack backtrace: CPU: 0 UID: 0 PID: 11577 Comm: syz.7.1110 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2059 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2191 check_prev_add kernel/locking/lockdep.c:3181 [inline] check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x15ff/0x2e50 kernel/locking/lockdep.c:5254 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5908 __fs_reclaim_acquire mm/page_alloc.c:4433 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4447 might_alloc include/linux/sched/mm.h:314 [inline] slab_pre_alloc_hook mm/slub.c:4636 [inline] slab_alloc_node mm/slub.c:4974 [inline] __do_kmalloc_node mm/slub.c:5413 [inline] __kmalloc_noprof+0xbc/0x710 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] btrfs_calc_avail_data_space fs/btrfs/super.c:1631 [inline] btrfs_statfs+0xc2a/0x1b40 fs/btrfs/super.c:1781 statfs_by_dentry fs/statfs.c:66 [inline] vfs_statfs+0x147/0x2d0 fs/statfs.c:90 loop_get_discard_config drivers/block/loop.c:774 [inline] loop_update_limits+0x375/0x920 drivers/block/loop.c:984 loop_configure+0x7d2/0xdc0 drivers/block/loop.c:1084 lo_ioctl+0xad5/0x2150 drivers/block/loop.c:1564 blkdev_ioctl+0x5e3/0x740 block/ioctl.c:798 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x510 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3bf279e0d9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f3bf36b4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f3bf2a26180 RCX: 00007f3bf279e0d9 RDX: 00002000000005c0 RSI: 0000000000004c0a RDI: 0000000000000008 RBP: 00007f3bf2835024 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3bf2a26218 R14: 00007f3bf2a26180 R15: 00007ffd1bede9c8 --- 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 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