From: Aili Yao <yaoaili@kingsoft.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>, <akpm@linux-foundation.org>,
<naoya.horiguchi@nec.com>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>, <yangfeng1@kingsoft.com>,
<sunhao2@kingsoft.com>, Oscar Salvador <osalvador@suse.de>,
Mike Kravetz <mike.kravetz@oracle.com>, <yaoaili@kingsoft.com>
Subject: Re: [PATCH v3] mm/gup: check page posion status for coredump.
Date: Mon, 22 Mar 2021 11:40:23 +0800 [thread overview]
Message-ID: <20210322114023.79140596@alex-virtual-machine> (raw)
In-Reply-To: <20210320003516.GC3420@casper.infradead.org>
On Sat, 20 Mar 2021 00:35:16 +0000
Matthew Wilcox <willy@infradead.org> wrote:
> On Fri, Mar 19, 2021 at 10:44:37AM +0800, Aili Yao wrote:
> > +++ b/mm/gup.c
> > @@ -1536,6 +1536,10 @@ struct page *get_dump_page(unsigned long addr)
> > FOLL_FORCE | FOLL_DUMP | FOLL_GET);
> > if (locked)
> > mmap_read_unlock(mm);
> > +
> > + if (ret == 1 && is_page_poisoned(page))
> > + return NULL;
> > +
> > return (ret == 1) ? page : NULL;
> > }
> > #endif /* CONFIG_ELF_CORE */
> > diff --git a/mm/internal.h b/mm/internal.h
> > index 25d2b2439..902d993 100644
> > --- a/mm/internal.h
> > +++ b/mm/internal.h
> > @@ -97,6 +97,27 @@ static inline void set_page_refcounted(struct page *page)
> > set_page_count(page, 1);
> > }
> >
> > +/*
> > + * When kernel touch the user page, the user page may be have been marked
> > + * poison but still mapped in user space, if without this page, the kernel
> > + * can guarantee the data integrity and operation success, the kernel is
> > + * better to check the posion status and avoid touching it, be good not to
> > + * panic, coredump for process fatal signal is a sample case matching this
> > + * scenario. Or if kernel can't guarantee the data integrity, it's better
> > + * not to call this function, let kernel touch the poison page and get to
> > + * panic.
> > + */
> > +static inline bool is_page_poisoned(struct page *page)
> > +{
> > + if (page != NULL) {
>
> Why are you checking page for NULL here? How can it possibly be NULL?
For this get_dump_page() case, it can't be NULL, I thougt may other place
will call this function and may not guarantee this, But yes, kernel is a more
safer place and checking page NULL is not a common behavior.
Better to remove it, Thanks you very much for pointing this!
> > + if (PageHWPoison(page))
> > + return true;
> > + else if (PageHuge(page) && PageHWPoison(compound_head(page)))
> > + return true;
> > + }
> > + return 0;
> > +}
> > +
> > extern unsigned long highest_memmap_pfn;
> >
> > /*
> > --
> > 1.8.3.1
> >
> >
--
Thanks!
Aili Yao
next prev parent reply other threads:[~2021-03-22 3:40 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 8:37 [PATCH] mm/gup: check page posion status for coredump Aili Yao
2021-03-17 9:12 ` David Hildenbrand
2021-03-18 3:15 ` Aili Yao
2021-03-18 3:18 ` [PATCH v2] " Aili Yao
2021-03-18 4:46 ` [PATCH] " Matthew Wilcox
2021-03-18 5:34 ` Aili Yao
2021-03-19 2:44 ` [PATCH v3] " Aili Yao
2021-03-20 0:35 ` Matthew Wilcox
2021-03-22 3:40 ` Aili Yao [this message]
2021-03-22 11:33 ` [PATCH v5] mm/gup: check page hwposion " Aili Yao
2021-03-26 14:09 ` David Hildenbrand
2021-03-26 14:22 ` David Hildenbrand
2021-03-31 1:52 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-31 2:43 ` Aili Yao
2021-03-31 4:32 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-31 6:44 ` David Hildenbrand
2021-03-31 7:07 ` Aili Yao
2021-04-01 2:31 ` Aili Yao
2021-04-06 2:23 ` [PATCH v6] mm/gup: check page hwpoison status for memory recovery failures Aili Yao
2021-04-06 2:41 ` [PATCH v7] " Aili Yao
2021-04-07 1:54 ` HORIGUCHI NAOYA(堀口 直也)
2021-04-07 7:48 ` Aili Yao
2021-05-10 3:13 ` Aili Yao
2021-03-31 6:07 ` [PATCH v5] mm/gup: check page hwposion status for coredump Matthew Wilcox
2021-03-31 6:53 ` HORIGUCHI NAOYA(堀口 直也)
2021-03-31 7:05 ` David Hildenbrand
2021-03-18 8:14 ` [PATCH] mm/gup: check page posion " David Hildenbrand
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