From d3378e86d1822b6d0bebfbc18a8348691c05dfa0 Mon Sep 17 00:00:00 2001 From: Aili Yao Date: Fri, 9 Apr 2021 13:27:19 -0700 Subject: [PATCH] mm/gup: check page posion status for coredump. When we do coredump for user process signal, this may be an 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 poison status in get_dump_page(), and if TRUE, return NULL. There maybe other scenario that is also better to check the posion status and not to panic, so make a wrapper for this check, Thanks to David's suggestion(). [akpm@linux-foundation.org: s/0/false/] [yaoaili@kingsoft.com: is_page_poisoned() arg cannot be null, per Matthew] Link: https://lkml.kernel.org/r/20210322115233.05e4e82a@alex-virtual-machine Link: https://lkml.kernel.org/r/20210319104437.6f30e80d@alex-virtual-machine Signed-off-by: Aili Yao Cc: David Hildenbrand Cc: Matthew Wilcox Cc: Naoya Horiguchi Cc: Oscar Salvador Cc: Mike Kravetz Cc: Aili Yao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/gup.c | 4 ++++ mm/internal.h | 20 ++++++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index e40579624f10..ef7d2da9f03f 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1535,6 +1535,10 @@ 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 1432feec62df..cb3c5e0a7799 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_poisoned(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; /* -- 2.39.5