linux-kernel - Re: [syzbot] [mm?] WARNING in copy

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Message-ID: <20250828131235.6007-1-hdanton@sina.com>
Date: Thu, 28 Aug 2025 21:12:34 +0800
From: Hillf Danton <hdanton@...a.com>
To: David Hildenbrand <david@...hat.com>
Cc: syzbot <syzbot+69c74d38464686431506@...kaller.appspotmail.com>,
	akpm@...ux-foundation.org,
	kees@...nel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	peterz@...radead.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] WARNING in copy_process

On Mon, 25 Aug 2025 17:50:15 +0200 David Hildenbrand wrote:
> On 25.08.25 05:00, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    41cd3fd15263 Merge tag 'pci-v6.17-fixes-2' of git://git.ke..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13d8b3bc580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=fecbb496f75d3d61
> > dashboard link: https://syzkaller.appspot.com/bug?extid=69c74d38464686431506
> > 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/ea83f558e101/disk-41cd3fd1.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/a35b75cdd97b/vmlinux-41cd3fd1.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/37d76e9636c2/bzImage-41cd3fd1.xz
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+69c74d38464686431506@...kaller.appspotmail.com
> > 
> > oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0-1,oom_memcg=/syz1,task_memcg=/syz1,task=syz.1.3237,pid=23388,uid=0
> > Memory cgroup out of memory: Killed process 23388 (syz.1.3237) total-vm:101828kB, anon-rss:940kB, file-rss:21532kB, shmem-rss:0kB, UID:0 pgtables:116kB oom_score_adj:1000
> 
> Here we are killing 23388 (syz.1.3237)
> 
> > ------------[ cut here ]------------
> > pvqspinlock: lock 0xffff88803512c0c0 has corrupted value 0x0!
> > WARNING: CPU: 0 PID: 23388 at kernel/locking/qspinlock_paravirt.h:504 __pv_queued_spin_unlock_slowpath+0x237/0x330 kernel/locking/qspinlock_paravirt.h:504
> > Modules linked in:
> > CPU: 0 UID: 0 PID: 23388 Comm: syz.1.3237 Tainted: G     U              syzkaller #0 PREEMPT(full)
> 
> And here we are still in the process ...
> 
> > Tainted: [U]=USER
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
> > RIP: 0010:__pv_queued_spin_unlock_slowpath+0x237/0x330 kernel/locking/qspinlock_paravirt.h:504
> > Code: 03 0f b6 14 02 4c 89 e8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 67 41 8b 55 00 4c 89 ee 48 c7 c7 00 81 ad 8b e8 fa aa e6 f5 90 <0f> 0b 90 90 e9 64 ff ff ff 90 0f 0b 48 89 df 4c 89 04 24 e8 71 15
> > RSP: 0018:ffffc9000e9c79c8 EFLAGS: 00010286
> > RAX: 0000000000000000 RBX: ffff88803512c0c0 RCX: ffffffff817a02c8
> > RDX: ffff88802fa9bc00 RSI: ffffffff817a02d5 RDI: 0000000000000001
> > RBP: ffff88803512c0c8 R08: 0000000000000001 R09: 0000000000000000
> > R10: 0000000000000000 R11: 00000000000d4550 R12: ffff88803512c0d0
> > R13: ffff88803512c0c0 R14: 00000000003d0f00 R15: ffff88802ab43c00
> > FS:  0000555568154500(0000) GS:ffff8881246c4000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007f86cc8e86ec CR3: 0000000060c0e000 CR4: 00000000003526f0
> > Call Trace:
> >   <TASK>
> >   __raw_callee_save___pv_queued_spin_unlock_slowpath+0x15/0x30
> >   .slowpath+0x9/0x18
> >   pv_queued_spin_unlock arch/x86/include/asm/paravirt.h:562 [inline]
> >   queued_spin_unlock arch/x86/include/asm/qspinlock.h:57 [inline]
> >   do_raw_spin_unlock+0x172/0x230 kernel/locking/spinlock_debug.c:142
> >   __raw_spin_unlock include/linux/spinlock_api_smp.h:142 [inline]
> >   _raw_spin_unlock+0x1e/0x50 kernel/locking/spinlock.c:186
> >   spin_unlock include/linux/spinlock.h:391 [inline]
> 
> ... busy during clone.
> 
> I assume that it is 23388 calling clone() and not getting cloned (it 
> should not get scheduled yet).
> 
> So likely, the OOM is shooting something down that kernel_clone() still 
> depends on ... maybe?
> 
Difficult to understand the oom shot given tasklist_lock held for write
also in release_task(), weird.