Re: [syzbot] [kernel?] INFO: task hung in vfs_coredump (2)

[syzbot <syzbot+6ed94e81a1492fe1d512@syzkaller.appspotmail.com>]

Hello,

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

INFO: task syz.0.17:6434 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:28424 pid:6434  tgid:6432  ppid:6327   task_flags:0x400640 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5298 [inline]
 __schedule+0xfee/0x6120 kernel/sched/core.c:6911
 __schedule_loop kernel/sched/core.c:6993 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7008
 schedule_timeout+0x1b2/0x280 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common+0x2e7/0x4c0 kernel/sched/completion.c:121
 wait_for_common kernel/sched/completion.c:132 [inline]
 wait_for_completion_state+0x1c/0x40 kernel/sched/completion.c:269
 coredump_wait fs/coredump.c:534 [inline]
 vfs_coredump+0x80d/0x5570 fs/coredump.c:1197
 get_signal+0x1f2a/0x21e0 kernel/signal.c:3019
 arch_do_signal_or_restart+0x91/0x770 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x4a0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x668/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f994879af39
RSP: 002b:00007f99497010e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f9948a06098 RCX: 00007f994879af39
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f9948a0609c
RBP: 00007f9948a06090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9948a06128 R14: 00007ffd4eff3890 R15: 00007ffd4eff3978
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
 #0: ffffffff8e5ce2e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8e5ce2e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8e5ce2e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
2 locks held by getty/5581:
 #0: ffff888037b420a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211
1 lock held by syz.0.17/6433:
1 lock held by syz.1.18/6456:
1 lock held by syz.2.19/6480:
5 locks held by syz.3.20/6510:
1 lock held by syz.4.21/6540:
1 lock held by syz.5.22/6569:
2 locks held by syz.6.23/6606:
1 lock held by syz.7.24/6637:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x1d7/0x230 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
 watchdog+0xd25/0x1050 kernel/hung_task.c:515
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 6480 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:memset_orig+0x3a/0xb0 arch/x86/lib/memset_64.S:71
Code: 01 48 0f af c1 41 89 f9 41 83 e1 07 75 74 48 89 d1 48 c1 e9 06 74 39 66 0f 1f 84 00 00 00 00 00 48 ff c9 48 89 07 48 89 47 08 <48> 89 47 10 48 89 47 18 48 89 47 20 48 89 47 28 48 89 47 30 48 89
RSP: 0018:ffffc90002e77028 EFLAGS: 00000206
RAX: 0000000000000000 RBX: ffffc90002e77240 RCX: 0000000000000024
RDX: 0000000000001000 RSI: 0000000000000000 RDI: ffff88805e0546c0
RBP: 0000000000001000 R08: 0000000000000001 R09: 0000000000000000
R10: ffff88805e054000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffc90002e77248 R14: 0000000000001000 R15: 0000000000000000
FS:  00007fd2a88bb6c0(0000) GS:ffff88812472f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555882e94e8 CR3: 000000007846e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 zero_to_iter lib/iov_iter.c:461 [inline]
 iterate_kvec include/linux/iov_iter.h:86 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:308 [inline]
 iterate_and_advance include/linux/iov_iter.h:330 [inline]
 iov_iter_zero+0x9bd/0x15b0 lib/iov_iter.c:467
 hugetlbfs_read_iter+0x6e3/0x8c0 fs/hugetlbfs/inode.c:277
 __kernel_read+0x397/0xac0 fs/read_write.c:532
 integrity_kernel_read+0x7e/0xb0 security/integrity/iint.c:28
 ima_calc_file_hash_tfm+0x25e/0x350 security/integrity/ima/ima_crypto.c:480
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
 ima_calc_file_hash+0x18c/0x480 security/integrity/ima/ima_crypto.c:568
 ima_collect_measurement+0x887/0xa40 security/integrity/ima/ima_api.c:295
 process_measurement+0xdfe/0x2350 security/integrity/ima/ima_main.c:407
 ima_file_mmap+0x1c4/0x1f0 security/integrity/ima/ima_main.c:505
 security_mmap_file+0x278/0x9b0 security/security.c:2504
 vm_mmap_pgoff+0xec/0x470 mm/util.c:575
 ksys_mmap_pgoff+0x273/0x650 mm/mmap.c:605
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
 __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
 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: 0033:0x7fd2a799af39
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:00007fd2a88bb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fd2a7c05fa0 RCX: 00007fd2a799af39
RDX: 00004000000000df RSI: 0000004000000001 RDI: 0000000000000008
RBP: 00007fd2a7a2fee0 R08: ffffffffffffffff R09: 0000300000000000
R10: 0000000000040eb1 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd2a7c06038 R14: 00007fd2a7c05fa0 R15: 00007fff04aad838
 </TASK>


Tested on:

commit:         113ae7b4 Merge tag 'hwmon-for-v7.0-rc5' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13e2ccba580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c91defb609dfc805
dashboard link: https://syzkaller.appspot.com/bug?extid=6ed94e81a1492fe1d512
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1082ccba580000