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

[Miaohe Lin <linmiaohe@huawei.com>]

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);

> 
>> 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
>>
> 
> I guess cc:stable.  It looks old?  Can you help to identify the Fixes:
> target?

Since memory unpoison is only used for testing and users usually won't pass in a offlined pfn (memory
offline itself should be rare too). So I think this doesn't deserve cc statble. But If a Fixes tag is
required, I think it should be:

Fixes: f165b378bbdf ("mm: uninitialized struct page poisoning sanity checking")

Thanks.
.