Message-ID: <ed109c41666a9a4257006431449ff94b342bac24.camel@kernel.org>
Date: Thu, 17 Oct 2024 10:50:44 -0400
From: Jeff Layton <jlayton@...nel.org>
To: syzbot <syzbot+e7baeb70aa00c22ed45e@...kaller.appspotmail.com>, 
	Dai.Ngo@...cle.com, chuck.lever@...cle.com, linux-kernel@...r.kernel.org, 
	linux-nfs@...r.kernel.org, neilb@...e.de, okorniev@...hat.com, 
	syzkaller-bugs@...glegroups.com, tom@...pey.com
Subject: Re: [syzbot] [nfs?] INFO: task hung in nfsd_nl_threads_set_doit

On Wed, 2024-10-09 at 12:06 -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    75b607fab38d Merge tag 'sched_ext-for-6.12-rc2-fixes' of g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15e49f9f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=667b897270c8ae6
> dashboard link: https://syzkaller.appspot.com/bug?extid=e7baeb70aa00c22ed45e
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/a7759a7b0126/disk-75b607fa.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/734e9758ae9d/vmlinux-75b607fa.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e23bee69aa18/bzImage-75b607fa.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e7baeb70aa00c22ed45e@...kaller.appspotmail.com
> 
> INFO: task syz.2.8721:28280 blocked for more than 143 seconds.
>       Not tainted 6.12.0-rc2-syzkaller-00058-g75b607fab38d #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.2.8721      state:D stack:24848 pid:28280 tgid:28278 ppid:21973  flags:0x00000004
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5322 [inline]
>  __schedule+0xef5/0x5750 kernel/sched/core.c:6682
>  __schedule_loop kernel/sched/core.c:6759 [inline]
>  schedule+0xe7/0x350 kernel/sched/core.c:6774
>  schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6831
>  __mutex_lock_common kernel/locking/mutex.c:684 [inline]
>  __mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752
>  nfsd_nl_threads_set_doit+0x694/0xbe0 fs/nfsd/nfsctl.c:1671
>  genl_family_rcv_msg_doit+0x202/0x2f0 net/netlink/genetlink.c:1115
>  genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
>  genl_rcv_msg+0x565/0x800 net/netlink/genetlink.c:1210
>  netlink_rcv_skb+0x165/0x410 net/netlink/af_netlink.c:2550
>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
>  netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
>  netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357
>  netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901
>  sock_sendmsg_nosec net/socket.c:729 [inline]
>  __sock_sendmsg net/socket.c:744 [inline]
>  ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2602
>  ___sys_sendmsg+0x135/0x1e0 net/socket.c:2656
>  __sys_sendmsg+0x117/0x1f0 net/socket.c:2685
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f5c35f7dff9
> RSP: 002b:00007f5c36d61038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007f5c36136058 RCX: 00007f5c35f7dff9
> RDX: 0000000000008004 RSI: 0000000020000140 RDI: 0000000000000004
> RBP: 00007f5c35ff0296 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 00007f5c36136058 R15: 00007ffcc9b7fe28
>  </TASK>
> 
> Showing all locks held in the system:
> 2 locks held by kworker/u8:1/12:
>  #0: ffff88801ac89148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1212/0x1b30 kernel/workqueue.c:3204
>  #1: ffffc90000117d80 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x8bb/0x1b30 kernel/workqueue.c:3205
> 1 lock held by khungtaskd/30:
>  #0: ffffffff8ddb7800 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
>  #0: ffffffff8ddb7800 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
>  #0: ffffffff8ddb7800 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x7f/0x390 kernel/locking/lockdep.c:6720
> 3 locks held by kworker/u8:9/3046:
> 2 locks held by getty/4992:
>  #0: ffff88814ba810a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
>  #1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xfba/0x1480 drivers/tty/n_tty.c:2211
> 1 lock held by syz-executor/5223:
> 2 locks held by syz-executor/18087:
>  #0: ffff888066cea0e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
>  #0: ffff888066cea0e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
>  #0: ffff888066cea0e0 (&type->s_umount_key#49){++++}-{3:3}, at: deactivate_super+0xd6/0x100 fs/super.c:505
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:625
> 1 lock held by syz.1.7378/23757:
> 2 locks held by syz.2.8721/28279:
>  #0: ffffffff8fb61250 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_listener_set_doit+0xe3/0x1b40 fs/nfsd/nfsctl.c:1964
> 2 locks held by syz.2.8721/28280:
>  #0: ffffffff8fb61250 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_threads_set_doit+0x694/0xbe0 fs/nfsd/nfsctl.c:1671
> 2 locks held by syz-executor/28836:
>  #0: ffff8880543960e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
>  #0: ffff8880543960e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
>  #0: ffff8880543960e0 (&type->s_umount_key#49){++++}-{3:3}, at: deactivate_super+0xd6/0x100 fs/super.c:505
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:625
> 2 locks held by syz.0.8904/29170:
>  #0: ffff88807b2260e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
>  #0: ffff88807b2260e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
>  #0: ffff88807b2260e0 (&type->s_umount_key#49){++++}-{3:3}, at: deactivate_super+0xd6/0x100 fs/super.c:505
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:625
> 2 locks held by syz-executor/29233:
>  #0: ffff88807bb580e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
>  #0: ffff88807bb580e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
>  #0: ffff88807bb580e0 (&type->s_umount_key#49){++++}-{3:3}, at: deactivate_super+0xd6/0x100 fs/super.c:505
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:625
> 2 locks held by syz.2.8947/29381:
>  #0: ffffffff8fb61250 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_nl_threads_set_doit+0x694/0xbe0 fs/nfsd/nfsctl.c:1671
> 2 locks held by syz-executor/29390:
>  #0: ffff88802e63a0e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
>  #0: ffff88802e63a0e0 (&type->s_umount_key#49){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
>  #0: ffff88802e63a0e0 (&type->s_umount_key#49){++++}-{3:3}, at: deactivate_super+0xd6/0x100 fs/super.c:505
>  #1: ffffffff8e1d1868 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:625
> 2 locks held by syz-executor/29649:
> 1 lock held by syz.1.9007/29775:
> 2 locks held by syz.1.9027/29961:
> 1 lock held by syz.0.9047/30028:
> 1 lock held by syz.2.9046/30029:
> 
> =============================================
> 
> NMI backtrace for cpu 1
> CPU: 1 UID: 0 PID: 30 Comm: khungtaskd Not tainted 6.12.0-rc2-syzkaller-00058-g75b607fab38d #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
>  nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
>  nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
>  trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
>  watchdog+0xf0c/0x1240 kernel/hung_task.c:379
>  kthread+0x2c1/0x3a0 kernel/kthread.c:389
>  ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>  </TASK>
> Sending NMI from CPU 1 to CPUs 0:
> NMI backtrace for cpu 0
> CPU: 0 UID: 0 PID: 23757 Comm: syz.1.7378 Not tainted 6.12.0-rc2-syzkaller-00058-g75b607fab38d #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> RIP: 0010:kernel_fpu_begin_mask+0x17b/0x270 arch/x86/kernel/fpu/core.c:443
> Code: 01 31 ff 89 de e8 45 b6 59 00 85 db 0f 85 ce 00 00 00 e8 f8 b3 59 00 48 b8 00 00 00 00 00 fc ff df 48 c7 44 05 00 00 00 00 00 <48> 8b 44 24 58 65 48 2b 04 25 28 00 00 00 0f 85 c6 00 00 00 48 83
> RSP: 0018:ffffc9000ac3f3d8 EFLAGS: 00000246
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000ac4d000
> RDX: 0000000000040000 RSI: ffffffff813304c8 RDI: 0000000000000005
> RBP: 1ffff92001587e7b R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
> R13: 0000000000001000 R14: 0000000000001000 R15: ffffc9000ac3f500
> FS:  00007faf7f5ea6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fbfabe67d60 CR3: 000000002859c000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <NMI>
>  </NMI>
>  <TASK>
>  kernel_fpu_begin arch/x86/include/asm/fpu/api.h:42 [inline]
>  _sha256_update arch/x86/crypto/sha256_ssse3_glue.c:73 [inline]
>  _sha256_update+0xb7/0x220 arch/x86/crypto/sha256_ssse3_glue.c:58
>  ima_calc_file_hash_tfm+0x302/0x3e0 security/integrity/ima/ima_crypto.c:491
>  ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
>  ima_calc_file_hash+0x1ba/0x490 security/integrity/ima/ima_crypto.c:568
>  ima_collect_measurement+0x8a7/0xa10 security/integrity/ima/ima_api.c:293
>  process_measurement+0x1271/0x2370 security/integrity/ima/ima_main.c:372
>  ima_file_mmap+0x1b1/0x1d0 security/integrity/ima/ima_main.c:462
>  security_mmap_file+0x8bd/0x990 security/security.c:2977
>  vm_mmap_pgoff+0xdb/0x360 mm/util.c:584
>  ksys_mmap_pgoff+0x1c8/0x5c0 mm/mmap.c:542
>  __do_sys_mmap arch/x86/kernel/sys_x86_64.c:86 [inline]
>  __se_sys_mmap arch/x86/kernel/sys_x86_64.c:79 [inline]
>  __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:79
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7faf7e77dff9
> 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:00007faf7f5ea038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
> RAX: ffffffffffffffda RBX: 00007faf7e935f80 RCX: 00007faf7e77dff9
> RDX: 00004000000000df RSI: 0000002000000004 RDI: 0000000000000002
> RBP: 00007faf7e7f0296 R08: 0000000000000404 R09: 0000300000000000
> R10: 0000000000040eb2 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 00007faf7e935f80 R15: 00007fffb2184568
>  </TASK>
> 
> 
> ---
> 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 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


We've had a number of reports of this. To be clear, we currently
consider these problems to be low-priority since they require abusing
privileged interfaces. Still, I've opened this bug at kernel.org to
track the issue:

    https://bugzilla.kernel.org/show_bug.cgi?id=219396

-- 
Jeff Layton <jlayton@...nel.org>

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