Commit 373c4557 authored Nov 14, 2017 by Jann Horn Committed by Linus Torvalds Nov 15, 2017

mm/pagewalk.c: report holes in hugetlb ranges



This matters at least for the mincore syscall, which will otherwise copy
uninitialized memory from the page allocator to userspace.  It is
probably also a correctness error for /proc/$pid/pagemap, but I haven't
tested that.

Removing the `walk->hugetlb_entry` condition in walk_hugetlb_range() has
no effect because the caller already checks for that.

This only reports holes in hugetlb ranges to callers who have specified
a hugetlb_entry callback.

This issue was found using an AFL-based fuzzer.

v2:
 - don't crash on ->pte_hole==NULL (Andrew Morton)
 - add Cc stable (Andrew Morton)

Fixes: 1e25a271 ("mincore: apply page table walker on do_mincore()")
Signed-off-by: Jann Horn <jannh@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5bbcc0f5

mm/pagewalk.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -188,8 +188,12 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
		do {
		next = hugetlb_entry_end(h, addr, end);
		pte = huge_pte_offset(walk->mm, addr & hmask, sz);
		if (pte && walk->hugetlb_entry)

		if (pte)
		err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
		else if (walk->pte_hole)
		err = walk->pte_hole(addr, next, walk);

		if (err)
		break;
		} while (addr = next, addr != end);

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