[PATCH] Fix hugepage crash on failing mmap() (c7546f8f) · Commits · 戴 / test

This patch fixes a crash in the hugepage code. unmap_hugepage_area() was assuming that (due to prefault) PTEs must exist for all the area in question. However, this may not be the case, if mmap() encounters an error before the prefault and calls unmap_region() to clean up any partial mapping. Depending on the hugepage configuration, this crash can be triggered by an unpriveleged user. Signed-off-by:

David Gibson <david@gibson.dropbear.id.au> Cc: William Lee Irwin III <wli@holomorphy.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

mm/hugetlb.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -301,6 +301,7 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
		{
		struct mm_struct *mm = vma->vm_mm;
		unsigned long address;
		pte_t *ptep;
		pte_t pte;
		struct page *page;

		@@ -309,9 +310,17 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
		BUG_ON(end & ~HPAGE_MASK);

		for (address = start; address < end; address += HPAGE_SIZE) {
		pte = huge_ptep_get_and_clear(mm, address, huge_pte_offset(mm, address));
		ptep = huge_pte_offset(mm, address);
		if (! ptep)
		/* This can happen on truncate, or if an
		* mmap() is aborted due to an error before
		* the prefault */
		continue;

		pte = huge_ptep_get_and_clear(mm, address, ptep);
		if (pte_none(pte))
		continue;

		page = pte_page(pte);
		put_page(page);
		}

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