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mm/pagewalk.c: report holes in hugetlb ranges

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commit 373c4557d2 upstream.

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)

Changed for 4.4/4.9 stable backport:
 - fix up conflict in the huge_pte_offset() call

Fixes: 1e25a271c8 ("mincore: apply page table walker on do_mincore()")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jann Horn
2017-11-14 01:03:44 +01:00
committed by Greg Kroah-Hartman
parent fae5947129
commit ceaec6e8cd
1 changed files with 5 additions and 1 deletions
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6
mm/pagewalk.c
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@@ -142,8 +142,12 @@ 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);
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);