Messages in this thread | | | From | David Hildenbrand <> | Subject | Re: [PATCH v5] mm/gup: check page hwposion status for coredump. | Date | Fri, 26 Mar 2021 15:09:18 +0100 |
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On 22.03.21 12:33, Aili Yao wrote: > When we do coredump for user process signal, this may be one SIGBUS signal > with BUS_MCEERR_AR or BUS_MCEERR_AO code, which means this signal is > resulted from ECC memory fail like SRAR or SRAO, we expect the memory > recovery work is finished correctly, then the get_dump_page() will not > return the error page as its process pte is set invalid by > memory_failure(). > > But memory_failure() may fail, and the process's related pte may not be > correctly set invalid, for current code, we will return the poison page, > get it dumped, and then lead to system panic as its in kernel code. > > So check the hwpoison status in get_dump_page(), and if TRUE, return NULL. > > There maybe other scenario that is also better to check hwposion status > and not to panic, so make a wrapper for this check, Thanks to David's > suggestion(<david@redhat.com>). > > Link: https://lkml.kernel.org/r/20210319104437.6f30e80d@alex-virtual-machine > Signed-off-by: Aili Yao <yaoaili@kingsoft.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Matthew Wilcox <willy@infradead.org> > Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Aili Yao <yaoaili@kingsoft.com> > Cc: stable@vger.kernel.org > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > mm/gup.c | 4 ++++ > mm/internal.h | 20 ++++++++++++++++++++ > 2 files changed, 24 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index e4c224c..6f7e1aa 100644 > --- a/mm/gup.c > +++ 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);
Thinking again, wouldn't we get -EFAULT from __get_user_pages_locked() when stumbling over a hwpoisoned page?
See __get_user_pages_locked()->__get_user_pages()->faultin_page():
handle_mm_fault()->vm_fault_to_errno(), which translates VM_FAULT_HWPOISON to -EFAULT, unless FOLL_HWPOISON is set (-> -EHWPOISON)
?
> + > + if (ret == 1 && is_page_hwpoison(page)) > + return NULL; > + > return (ret == 1) ? page : NULL; > } > #endif /* CONFIG_ELF_CORE */ > diff --git a/mm/internal.h b/mm/internal.h > index 25d2b2439..b751cef 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -97,6 +97,26 @@ 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_hwpoison(struct page *page) > +{ > + if (PageHWPoison(page)) > + return true; > + else if (PageHuge(page) && PageHWPoison(compound_head(page))) > + return true; > + > + return false; > +} > + > extern unsigned long highest_memmap_pfn; > > /* >
-- Thanks,
David / dhildenb
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