From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f80.google.com (mail-oo1-f80.google.com [209.85.161.80]) (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 172E13CB2E6 for ; Fri, 10 Apr 2026 17:24:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.80 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775841867; cv=none; b=C7rpBHCyitCQeXU/99aIl1WQ+ix1C7kK1kL4ajfZTCZlgivrXPgcTonOH7w1zPFbB08B4D7nLOwPTAf/nqnusMqrBdcIsGVrrujqwR98q6NJni7Tq/kPhvYxh4e2vPZLf/KphqbJOc/hGUH12RiUc5feASZ1iZW0A8aKvCG1Bqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775841867; c=relaxed/simple; bh=+gKTHxoxDMKo3u7evTWoh9TWfhwBQlT6ukGhjEx6wjA=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=sewrpy2/XDMYg3sCSHVyIrj/V6Y4FNa/hp8kcY4JjnkiHKK1zoS44wZ1+5siAFos8ZAn5zVPjrOHUsGLYFu5iawRbDZSXqtXpESISmYNW9Uo3CiAw+Nb86M5rBavnCpvarmCktJxR3BEKAJTGWY+BMo95dgliUIOURBoeQUucTE= 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=209.85.161.80 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-oo1-f80.google.com with SMTP id 006d021491bc7-66b612efb4aso3270734eaf.0 for ; Fri, 10 Apr 2026 10:24:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775841865; x=1776446665; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=1FOmNqJ3sPBDzLwH7LK8E0lSFhzB2S92n5VYz6A1mpM=; b=et67GKK8k66vG5uLZbrbDXkqjdrKZ22S8EIEjcPotqTHEdHY2bZ+SgDPXBsJLu/DAf aOjSxAfu0XPdCseIjeA+x3sUVSNqnSNES6P1H/aMLEPWgB+XUL5U09I1jXxb4c6485OU 5iFO9sRsGM1yr4j6HM7d5CJelnZdDVhsaXDarWQYoeZVrhhebhJktB8NJaOhV+sXllZN 0HoLPt5/mUTiO1e3wZR57sbWifuQyAxZVYpZdJoS8ebsu0G519Y+WJyrtGyEKr3AWs5S Bi3/SDoLOgSkmIx4zr91HnGbte/1HRK0K0d/m37OxMIdJqJsyQ54xjEG2rK5kaf/0Csa ty3g== X-Forwarded-Encrypted: i=1; AJvYcCUDmh3ymmXom2Eyq+O6BCdENtft7CJw3Qfp3ZvDlhpdqfV4kLFb65YUVLXNUDH/CXNzJoxXxIFVAFxPuII=@vger.kernel.org X-Gm-Message-State: AOJu0YwqLAESRSz8vDP5N4qQsRy2eI3URsRerdGjTjyrzDsjlQakhPY/ IwJTLreVUE+MuQ+O84Ax4Vu7ty11u6/dg0nlL5jR4riPCgCuNdHSaW1RUR9414des2s3W/ODYNb yQX06omA8Fd76yJDC371O7bbi338deVEo6TwlGkvbTItOw54mlXO0XQvrcpc= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:8406:b0:682:4005:5a56 with SMTP id 006d021491bc7-68a68d601b9mr2542571eaf.12.1775841865008; Fri, 10 Apr 2026 10:24:25 -0700 (PDT) Date: Fri, 10 Apr 2026 10:24:24 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69d93248.050a0220.3030df.002f.GAE@google.com> Subject: [syzbot] [cgroups?] possible deadlock in cgroup_kn_lock_live (2) From: syzbot To: cgroups@vger.kernel.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, mkoutny@suse.com, syzkaller-bugs@googlegroups.com, tj@kernel.org Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 591cd656a1bf Linux 7.0-rc7 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=138ddd02580000 kernel config: https://syzkaller.appspot.com/x/.config?x=64e78d99d9bf8b4c dashboard link: https://syzkaller.appspot.com/bug?extid=6dc923fb5b4671f0fcf0 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/bf0f027c93ec/disk-591cd656.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/60d829be17f4/vmlinux-591cd656.xz kernel image: https://storage.googleapis.com/syzbot-assets/673c009c7550/bzImage-591cd656.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+6dc923fb5b4671f0fcf0@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.1.1390/12323 is trying to acquire lock: ffffffff8e84a7c8 (cgroup_mutex){+.+.}-{4:4}, at: cgroup_lock include/linux/cgroup.h:394 [inline] ffffffff8e84a7c8 (cgroup_mutex){+.+.}-{4:4}, at: cgroup_kn_lock_live+0x116/0x520 kernel/cgroup/cgroup.c:1732 but task is already holding lock: ffff888059c1d5c0 (&type->i_mutex_dir_key#7){++++}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline] ffff888059c1d5c0 (&type->i_mutex_dir_key#7){++++}-{4:4}, at: vfs_rmdir fs/namei.c:5329 [inline] ffff888059c1d5c0 (&type->i_mutex_dir_key#7){++++}-{4:4}, at: vfs_rmdir+0xed/0x8a0 fs/namei.c:5317 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&type->i_mutex_dir_key#7){++++}-{4:4}: down_read+0x99/0x460 kernel/locking/rwsem.c:1537 inode_lock_shared include/linux/fs.h:1043 [inline] lookup_slow+0x42/0x70 fs/namei.c:1932 walk_component fs/namei.c:2279 [inline] lookup_last fs/namei.c:2786 [inline] path_lookupat+0x5e8/0xc40 fs/namei.c:2810 filename_lookup+0x202/0x590 fs/namei.c:2839 kern_path+0x37/0x50 fs/namei.c:3046 lookup_bdev+0xd8/0x280 block/bdev.c:1221 bdev_file_open_by_path+0x82/0x330 block/bdev.c:1094 add_device drivers/mtd/devices/block2mtd.c:279 [inline] block2mtd_setup2.isra.0+0x2ee/0xc70 drivers/mtd/devices/block2mtd.c:459 block2mtd_setup+0xbd/0xd0 drivers/mtd/devices/block2mtd.c:476 param_attr_store+0x199/0x300 kernel/params.c:589 module_attr_store+0x58/0x80 kernel/params.c:913 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6ac/0x1070 fs/read_write.c:688 ksys_write+0x12a/0x250 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (param_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 ieee80211_rate_control_ops_get net/mac80211/rate.c:223 [inline] rate_control_alloc net/mac80211/rate.c:269 [inline] ieee80211_init_rate_ctrl_alg+0x1df/0x3b0 net/mac80211/rate.c:1016 ieee80211_register_hw+0x2950/0x4140 net/mac80211/main.c:1544 mac80211_hwsim_new_radio+0x2847/0x57d0 drivers/net/wireless/virtual/mac80211_hwsim.c:5809 init_mac80211_hwsim+0x6db/0x7f0 drivers/net/wireless/virtual/mac80211_hwsim.c:7172 do_one_initcall+0x11d/0x760 init/main.c:1382 do_initcall_level init/main.c:1444 [inline] do_initcalls init/main.c:1460 [inline] do_basic_setup init/main.c:1479 [inline] kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692 kernel_init+0x1f/0x1e0 init/main.c:1582 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (rtnl_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 cgrp_css_online+0xa1/0x1f0 net/core/netprio_cgroup.c:157 online_css+0xb2/0x350 kernel/cgroup/cgroup.c:5739 css_create kernel/cgroup/cgroup.c:5827 [inline] cgroup_apply_control_enable+0x8bd/0xbd0 kernel/cgroup/cgroup.c:3390 cgroup_mkdir+0x57f/0x1330 kernel/cgroup/cgroup.c:6028 kernfs_iop_mkdir+0x111/0x190 fs/kernfs/dir.c:1273 vfs_mkdir+0x361/0x850 fs/namei.c:5239 filename_mkdirat+0x48b/0x5e0 fs/namei.c:5272 __do_sys_mkdirat fs/namei.c:5293 [inline] __se_sys_mkdirat fs/namei.c:5290 [inline] __x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5290 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (cgroup_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 cgroup_lock include/linux/cgroup.h:394 [inline] cgroup_kn_lock_live+0x116/0x520 kernel/cgroup/cgroup.c:1732 cgroup_rmdir+0x22/0x300 kernel/cgroup/cgroup.c:6305 kernfs_iop_rmdir+0x106/0x170 fs/kernfs/dir.c:1291 vfs_rmdir fs/namei.c:5344 [inline] vfs_rmdir+0x328/0x8a0 fs/namei.c:5317 filename_rmdir+0x31a/0x5c0 fs/namei.c:5399 __do_sys_rmdir fs/namei.c:5422 [inline] __se_sys_rmdir fs/namei.c:5419 [inline] __x64_sys_rmdir+0x46/0x70 fs/namei.c:5419 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: cgroup_mutex --> param_lock --> &type->i_mutex_dir_key#7 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&type->i_mutex_dir_key#7); lock(param_lock); lock(&type->i_mutex_dir_key#7); lock(cgroup_mutex); *** DEADLOCK *** 3 locks held by syz.1.1390/12323: #0: ffff88807fec2420 (sb_writers#10){.+.+}-{0:0}, at: filename_rmdir+0x1ff/0x5c0 fs/namei.c:5388 #1: ffff88805cae8148 (&type->i_mutex_dir_key#7/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1073 [inline] #1: ffff88805cae8148 (&type->i_mutex_dir_key#7/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2929 [inline] #1: ffff88805cae8148 (&type->i_mutex_dir_key#7/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2940 [inline] #1: ffff88805cae8148 (&type->i_mutex_dir_key#7/1){+.+.}-{4:4}, at: filename_rmdir+0x258/0x5c0 fs/namei.c:5392 #2: ffff888059c1d5c0 (&type->i_mutex_dir_key#7){++++}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline] #2: ffff888059c1d5c0 (&type->i_mutex_dir_key#7){++++}-{4:4}, at: vfs_rmdir fs/namei.c:5329 [inline] #2: ffff888059c1d5c0 (&type->i_mutex_dir_key#7){++++}-{4:4}, at: vfs_rmdir+0xed/0x8a0 fs/namei.c:5317 stack backtrace: CPU: 0 UID: 0 PID: 12323 Comm: syz.1.1390 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 cgroup_lock include/linux/cgroup.h:394 [inline] cgroup_kn_lock_live+0x116/0x520 kernel/cgroup/cgroup.c:1732 cgroup_rmdir+0x22/0x300 kernel/cgroup/cgroup.c:6305 kernfs_iop_rmdir+0x106/0x170 fs/kernfs/dir.c:1291 vfs_rmdir fs/namei.c:5344 [inline] vfs_rmdir+0x328/0x8a0 fs/namei.c:5317 filename_rmdir+0x31a/0x5c0 fs/namei.c:5399 __do_sys_rmdir fs/namei.c:5422 [inline] __se_sys_rmdir fs/namei.c:5419 [inline] __x64_sys_rmdir+0x46/0x70 fs/namei.c:5419 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f8142b9c819 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:00007f81439b7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000054 RAX: ffffffffffffffda RBX: 00007f8142e16180 RCX: 00007f8142b9c819 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000040 RBP: 00007f8142c32c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f8142e16218 R14: 00007f8142e16180 R15: 00007ffc92158f68 --- 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