linux-kernel - Re: [syzbot] [fs?] INFO: task hung in user_get

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Message-ID: <000000000000a896e8060a80d978@google.com>
Date:   Sun, 19 Nov 2023 04:53:03 -0800
From:   syzbot <syzbot+ba09f4a317431df6cddf@...kaller.appspotmail.com>
To:     linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        tintinm2017@...il.com
Subject: Re: [syzbot] [fs?] INFO: task hung in user_get_super (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in user_get_super

INFO: task syz-executor.0:6844 blocked for more than 143 seconds.
      Not tainted 6.7.0-rc1-syzkaller-00344-g037266a5f723 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.0  state:D stack:0     pid:6844  tgid:6842  ppid:6827   flags:0x00000005
Call trace:
 __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
 context_switch kernel/sched/core.c:5376 [inline]
 __schedule+0x1354/0x2360 kernel/sched/core.c:6688
 __schedule_loop kernel/sched/core.c:6763 [inline]
 schedule+0xb8/0x19c kernel/sched/core.c:6778
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6835
 rwsem_down_read_slowpath+0x57c/0xe58 kernel/locking/rwsem.c:1086
 __down_read_common kernel/locking/rwsem.c:1250 [inline]
 __down_read kernel/locking/rwsem.c:1263 [inline]
 down_read+0xa0/0x2fc kernel/locking/rwsem.c:1528
 __super_lock fs/super.c:58 [inline]
 super_lock+0x160/0x328 fs/super.c:117
 user_get_super+0xe8/0x1a0 fs/super.c:1062
 quotactl_block fs/quota/quota.c:890 [inline]
 __do_sys_quotactl fs/quota/quota.c:955 [inline]
 __se_sys_quotactl fs/quota/quota.c:917 [inline]
 __arm64_sys_quotactl+0x508/0xca0 fs/quota/quota.c:917
 __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
 el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffff80008e6b46c0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:300
2 locks held by getty/5857:
 #0: ffff0000d2bdf0a0 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff800094e702f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41c/0x1228 drivers/tty/n_tty.c:2201
1 lock held by syz-executor.0/6551:
1 lock held by syz-executor.0/6844:
 #0: ffff0000da0280e0 (&type->s_umount_key#52){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff0000da0280e0 (&type->s_umount_key#52){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117
1 lock held by syz-executor.0/6862:
 #0: ffff0000da0280e0 (&type->s_umount_key#52){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff0000da0280e0 (&type->s_umount_key#52){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117
1 lock held by syz-executor.0/6888:
 #0: ffff0000da0280e0 (&type->s_umount_key#52){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff0000da0280e0 (&type->s_umount_key#52){++++}-{3:3}, at: super_lock+0x160/0x328 fs/super.c:117

=============================================



Tested on:

commit:         037266a5 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=12cbee48e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=696dc362ad4818c4
dashboard link: https://syzkaller.appspot.com/bug?extid=ba09f4a317431df6cddf
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Note: no patches were applied.