Re: [PATCH v3] mm/gup: check page posion status for coredump.
From: Matthew Wilcox <willy@infradead.org>
Date: 2021-03-20 00:36:35
Also in:
lkml
On Fri, Mar 19, 2021 at 10:44:37AM +0800, Aili Yao wrote:
quoted hunk ↗ jump to hunk
+++ 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?
+ 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