[moderation] [kernel?] KCSAN: assert: race in dequeue_entities

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2004cef11ea0 Merge tag 'sched-core-2024-09-19' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123db69f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=8ca3e8282608fcd1
dashboard link: https://syzkaller.appspot.com/bug?extid=7432e11f6f8a36b54f9d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [andre...@igalia.com da...@stgolabs.net dvh...@infradead.org linux-...@vger.kernel.org mi...@redhat.com pet...@infradead.org tg...@linutronix.de]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/12edf669f5e6/disk-2004cef1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e9e27c004fd8/vmlinux-2004cef1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f172ce8b328e/bzImage-2004cef1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7432e1...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: assert: race in __block_task kernel/sched/sched.h:2634 [inline]
BUG: KCSAN: assert: race in dequeue_entities+0x6df/0x760 kernel/sched/fair.c:7168

race at unknown origin, with assert no writes to 0xffff8881001cb1e8 of 4 bytes by task 5632 on cpu 1:
__block_task kernel/sched/sched.h:2634 [inline]
dequeue_entities+0x6df/0x760 kernel/sched/fair.c:7168
pick_next_entity kernel/sched/fair.c:5618 [inline]
pick_task_fair kernel/sched/fair.c:8847 [inline]
pick_next_task_fair+0x7d/0x410 kernel/sched/fair.c:8867
__pick_next_task kernel/sched/core.c:5888 [inline]
pick_next_task kernel/sched/core.c:6410 [inline]
__schedule+0x27c/0x940 kernel/sched/core.c:6561
__schedule_loop kernel/sched/core.c:6684 [inline]
schedule+0x55/0xc0 kernel/sched/core.c:6699
futex_wait_queue kernel/futex/waitwake.c:370 [inline]
__futex_wait+0x141/0x290 kernel/futex/waitwake.c:669
futex_wait+0x99/0x1c0 kernel/futex/waitwake.c:697
do_futex+0x276/0x370 kernel/futex/syscalls.c:102
__do_sys_futex kernel/futex/syscalls.c:179 [inline]
__se_sys_futex+0x25d/0x3a0 kernel/futex/syscalls.c:160
__x64_sys_futex+0x78/0x90 kernel/futex/syscalls.c:160
x64_sys_call+0x23c4/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:203
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5632 Comm: syz.3.573 Tainted: G W 6.11.0-syzkaller-07337-g2004cef11ea0 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
==================================================================


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[Aleksandr Nogikh]

Hi Marco,

Are you aware of the reasons why this report is looking so strange? Is
everything WAI?

1) "race at unknown origin"
2) "assert:" in the title

--
Aleksandr

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[Dmitry Vyukov]

On Thu, 19 Sept 2024 at 23:33, 'Aleksandr Nogikh' via
syzkaller-upstream-moderation

<syzkaller-upst...@googlegroups.com> wrote:
>
> Hi Marco,
>
> Are you aware of the reasons why this report is looking so strange? Is
> everything WAI?
>
> 1) "race at unknown origin"
> 2) "assert:" in the title
>
> --
> Aleksandr

This is one of ASSERT_EXCLUSIVE_WRITER:

ASSERT_EXCLUSIVE_WRITER(p->on_rq);

and it happened 372 times.

#syz upstream

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