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mm/gup: take mmap_lock in get_dump_page()
Properly take the mmap_lock before calling into the GUP code from get_dump_page(); and play nice, allowing the GUP code to drop the mmap_lock if it has to sleep. As Linus pointed out, we don't actually need the VMA because __get_user_pages() will flush the dcache for us if necessary. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Link: http://lkml.kernel.org/r/20200827114932.3572699-7-jannh@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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16
mm/gup.c
16
mm/gup.c
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@ -1547,19 +1547,23 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
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* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
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* allowing a hole to be left in the corefile to save diskspace.
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*
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* Called without mmap_lock, but after all other threads have been killed.
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* Called without mmap_lock (takes and releases the mmap_lock by itself).
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*/
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#ifdef CONFIG_ELF_CORE
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struct page *get_dump_page(unsigned long addr)
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{
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struct vm_area_struct *vma;
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struct mm_struct *mm = current->mm;
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struct page *page;
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int locked = 1;
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int ret;
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if (__get_user_pages_locked(current->mm, addr, 1, &page, &vma, NULL,
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FOLL_FORCE | FOLL_DUMP | FOLL_GET) < 1)
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if (mmap_read_lock_killable(mm))
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return NULL;
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flush_cache_page(vma, addr, page_to_pfn(page));
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return page;
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ret = __get_user_pages_locked(mm, addr, 1, &page, NULL, &locked,
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FOLL_FORCE | FOLL_DUMP | FOLL_GET);
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if (locked)
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mmap_read_unlock(mm);
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return (ret == 1) ? page : NULL;
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}
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#endif /* CONFIG_ELF_CORE */
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