Re: [syzbot] WARNING: suspicious RCU usage in get_timespec64

[Thomas Gleixner]

On Sun, Apr 04 2021 at 12:05, syzbot wrote:

Cc + ...

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    5e46d1b7 reiserfs: update reiserfs_xattrs_initialized() co..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1125f831d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=78ef1d159159890
> dashboard link: https://syzkaller.appspot.com/bug?extid=88e4f02896967fe1ab0d
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+88e4f02896967fe1ab0d@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> =============================
> WARNING: suspicious RCU usage
> 5.12.0-rc5-syzkaller #0 Not tainted
> -----------------------------
> kernel/sched/core.c:8294 Illegal context switch in RCU-sched read-side critical section!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 2, debug_locks = 0
> 3 locks held by syz-executor.4/8418:
>  #0: 
> ffff8880751d2b28
>  (
> &p->pi_lock
> ){-.-.}-{2:2}
> , at: try_to_wake_up+0x98/0x14a0 kernel/sched/core.c:3345
>  #1: 
> ffff8880b9d35258
>  (
> &rq->lock
> ){-.-.}-{2:2}
> , at: rq_lock kernel/sched/sched.h:1321 [inline]
> , at: ttwu_queue kernel/sched/core.c:3184 [inline]
> , at: try_to_wake_up+0x5e6/0x14a0 kernel/sched/core.c:3464
>  #2: ffff8880b9d1f948 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_change+0x142/0x220 kernel/sched/psi.c:807
>
> stack backtrace:
> CPU: 0 PID: 8418 Comm: syz-executor.4 Not tainted 5.12.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>  ___might_sleep+0x266/0x2c0 kernel/sched/core.c:8294
>  __might_fault+0x6e/0x180 mm/memory.c:5018
>  _copy_from_user+0x27/0x180 lib/usercopy.c:13
>  copy_from_user include/linux/uaccess.h:192 [inline]
>  get_timespec64+0x75/0x220 kernel/time/time.c:787
>  __do_sys_clock_nanosleep kernel/time/posix-timers.c:1257 [inline]
>  __se_sys_clock_nanosleep kernel/time/posix-timers.c:1245 [inline]
>  __x64_sys_clock_nanosleep+0x1bb/0x430 kernel/time/posix-timers.c:1245
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x48a621
> Code: 24 0c 89 3c 24 48 89 4c 24 18 e8 aa e7 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 8b 74 24 0c 8b 3c 24 b8 e6 00 00 00 0f 05 <44> 89 c7 48 89 04 24 e8 e3 e7 ff ff 48 8b 04 24 eb 97 66 2e 0f 1f
> RSP: 002b:00007fffe59fbd50 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
> RAX: ffffffffffffffda RBX: 0000000000000294 RCX: 000000000048a621
> RDX: 00007fffe59fbd90 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 00007fffe59fbe2c R08: 0000000000000000 R09: 00007fffe5b8a090
> R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000032
> R13: 000000000005717a R14: 0000000000000003 R15: 00007fffe59fbe90
>
>
> ---
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>
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