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

[David Hildenbrand <david@redhat.com>]

On 15.07.24 08:23, Miaohe Lin wrote:
> On 2024/7/13 5:09, Andrew Morton wrote:
>> On Fri, 12 Jul 2024 14:42:49 +0800 Miaohe Lin <linmiaohe@huawei.com> 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.
>>
>> I'm not seeing the call path.  Is this BUG happening via
>>
>> static __always_inline void __ClearPage##uname(struct page *page)	\
>> {									\
>> 	VM_BUG_ON_PAGE(!Page##uname(page), page);			\
>> 	page->page_type |= PG_##lname;					\
>> }
>>
>> ?
>>
>> If so, where's the callsite?
> 
> It is BUG on PF_ANY():
> 
> PAGEFLAG(HWPoison, hwpoison, PF_ANY)
> 
> #define PF_ANY(page, enforce)	PF_POISONED_CHECK(page)
> 
> #define PF_POISONED_CHECK(page) ({					\
> 	VM_BUG_ON_PGFLAGS(PagePoisoned(page), page);		\
> 	page; })
> 
> #define	PAGE_POISON_PATTERN	-1l
> static inline int PagePoisoned(const struct page *page)
> {
> 	return READ_ONCE(page->flags) == PAGE_POISON_PATTERN;
> }
> 
> The offlined pages will have page->flags set to PAGE_POISON_PATTERN while pfn is still valid:
> 
> offline_pages
>    remove_pfn_range_from_zone
>      page_init_poison
>        memset(page, PAGE_POISON_PATTERN, size);

Worth noting that this happens after __offline_isolated_pages() marked 
the covering sections as offline.

Are we missing a pfn_to_online_page() check somewhere, or are we racing 
with offlining code that marks the section offline?

-- 
Cheers,

David / dhildenb