Re: [PATCH v2] mm/memory-failure: fix VM_BUG_ON_PAGE(PagePoisoned(page)) when unpoison memory

[David Hildenbrand]

On 23.12.24 03:55, Miaohe Lin wrote:
> On 2024/12/20 16:50, David Hildenbrand wrote:
> > On 20.12.24 03:35, Miaohe Lin wrote:
> > > On 2024/12/19 20:18, David Hildenbrand wrote:
> > > > On 19.12.24 12:52, Miaohe Lin wrote:
> > > > > When I did memory failure tests recently, below panic occurs:
> > > > >
> > > > > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(page))
> > > > > kernel BUG at include/linux/page-flags.h:616!
> > > > > Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
> > > > > CPU: 3 PID: 720 Comm: bash Not tainted 6.10.0-rc1-00195-g148743902568 #40
> > > > > RIP: 0010:unpoison_memory+0x2f3/0x590
> > > > > RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
> > > > > RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
> > > > > RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
> > > > > RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
> > > > > R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
> > > > > R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
> > > > > FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
> > > > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
> > > > > Call Trace:
> > > > >     <TASK>
> > > > >     unpoison_memory+0x2f3/0x590
> > > > >     simple_attr_write_xsigned.constprop.0.isra.0+0xb3/0x110
> > > > >     debugfs_attr_write+0x42/0x60
> > > > >     full_proxy_write+0x5b/0x80
> > > > >     vfs_write+0xd5/0x540
> > > > >     ksys_write+0x64/0xe0
> > > > >     do_syscall_64+0xb9/0x1d0
> > > > >     entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > > > > RIP: 0033:0x7f08f0314887
> > > > > RSP: 002b:00007ffece710078 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > > > > RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f08f0314887
> > > > > RDX: 0000000000000009 RSI: 0000564787a30410 RDI: 0000000000000001
> > > > > RBP: 0000564787a30410 R08: 000000000000fefe R09: 000000007fffffff
> > > > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000009
> > > > > R13: 00007f08f041b780 R14: 00007f08f0417600 R15: 00007f08f0416a00
> > > > >     </TASK>
> > > > > Modules linked in: hwpoison_inject
> > > > > ---[ end trace 0000000000000000 ]---
> > > > > RIP: 0010:unpoison_memory+0x2f3/0x590
> > > > > RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
> > > > > RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
> > > > > RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
> > > > > RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
> > > > > R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
> > > > > R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
> > > > > FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
> > > > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
> > > > > Kernel panic - not syncing: Fatal exception
> > > > > Kernel Offset: 0x31c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
> > > > > ---[ end Kernel panic - not syncing: Fatal exception ]---
> > > > >
> > > > > The root cause is that unpoison_memory() tries to check the PG_HWPoison
> > > > > flags of an uninitialized page. So VM_BUG_ON_PAGE(PagePoisoned(page)) is
> > > > > triggered. This can be reproduced by below steps:
> > > > > 1.Offline memory block:
> > > > >     echo offline > /sys/devices/system/memory/memory12/state
> > > > > 2.Get offlined memory pfn:
> > > > >     page-types -b n -rlN
> > > > > 3.Write pfn to unpoison-pfn
> > > > >     echo <pfn> > /sys/kernel/debug/hwpoison/unpoison-pfn
> > > > >
> > > > > Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> > > > > ---
> > > > > v2: Use pfn_to_online_page per David. Thanks.
> > > > > ---
> > > > >     mm/memory-failure.c | 14 +++++++++++---
> > > > >     1 file changed, 11 insertions(+), 3 deletions(-)
> > > > >
> > > > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> > > > > index a7b8ccd29b6f..02be0596ce67 100644
> > > > > --- a/mm/memory-failure.c
> > > > > +++ b/mm/memory-failure.c
> > > > > @@ -2556,10 +2556,18 @@ int unpoison_memory(unsigned long pfn)
> > > > >         static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
> > > > >                         DEFAULT_RATELIMIT_BURST);
> > > > >     -    if (!pfn_valid(pfn))
> > > > > -        return -ENXIO;
> > > > > +    p = pfn_to_online_page(pfn);
> > > > > +    if (!p) {
> > > > > +        struct dev_pagemap *pgmap;
> > > > >     -    p = pfn_to_page(pfn);
> > > > > +        if (!pfn_valid(pfn))
> > > > > +            return -ENXIO;
> > > > > +        pgmap = get_dev_pagemap(pfn, NULL);
> > > > > +        if (!pgmap)
> > > > > +            return -ENXIO;
> > > > > +        put_dev_pagemap(pgmap);
> > > > > +        p = pfn_to_page(pfn);
> > > > > +    }
> > > >
> > > > Hm, I wonder if we can do anything reasonable with ZONE_DEVICE pages here?
> > >
> > > All I can see in unpoison_memory() is folio_test_clear_hwpoison() for ZONE_DEVICE pages.
> >
> > IIRC, it can only be triggered via debugfs in special kernel configs. So chances are this was never ever actually run against a ZONE_DEVICE page.
>
> If ZONE_DEVICE pages are never expected, we can simply filter them out.

Looking into some details, I think we should just ignore ZONE_DEVICE for 
now, I'm pretty sure that it's not handled correctly.

So I suggest to fail if pfn_to_online_page() == NULL, just like 
soft_offline_page() would.

--
Cheers,

David / dhildenb