Re: [syzbot] [mm?] WARNING: locking bug in __set_page_owner (2)

[Andrew Morton]

On Thu, 9 Oct 2025 17:26:21 -0700 Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote:

> On Thu, Oct 9, 2025 at 4:52 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Thu, 09 Oct 2025 09:45:33 -0700 syzbot <syzbot+8259e1d0e3ae8ed0c490@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    2c95a756e0cf net: pse-pd: tps23881: Fix current measuremen..
> > > git tree:       net
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=16e1852f980000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=5bcbbf19237350b5
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=8259e1d0e3ae8ed0c490
> > > compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > Downloadable assets:
> > > disk image: https://storage.googleapis.com/syzbot-assets/8272657e4298/disk-2c95a756.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/4e53ba690f28/vmlinux-2c95a756.xz
> > > kernel image: https://storage.googleapis.com/syzbot-assets/6112d620d6fc/bzImage-2c95a756.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+8259e1d0e3ae8ed0c490@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > At 2c95a756e0cf, page_owner.c hasn't been modified in a couple of years.
> >
> > How can add_stack_record_to_list()'s spin_lock_irqsave() be "invalid
> > wait context"?  In NMI, yes, but the trace doesn't indicate that we're
> > in an NMI.
> >
> > Confused.  I'm suspecting BPF involvement.  Cc'ed for help, please.
> 
> The attached patch should fix it.
> There are different options, but this one is the simplest.

Cool, thanks.

> From: Alexei Starovoitov <ast@xxxxxxxxxx>
> Subject: mm: don't spin in add_stack_record when gfp flags don't allow
> Date: Thu, 9 Oct 2025 17:15:13 -0700
> 
> syzbot was able to find the following path:
>   add_stack_record_to_list mm/page_owner.c:182 [inline]
>   inc_stack_record_count mm/page_owner.c:214 [inline]
>   __set_page_owner+0x2c3/0x4a0 mm/page_owner.c:333
>   set_page_owner include/linux/page_owner.h:32 [inline]
>   post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
>   prep_new_page mm/page_alloc.c:1859 [inline]
>   get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
>   alloc_pages_nolock_noprof+0x94/0x120 mm/page_alloc.c:7554
> 
> Don't spin in add_stack_record_to_list() when it is called
> from *_nolock() context.

Seems 6.18 will need this.  Do you think it is needed in earlier kernel
versions?