diff options
| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2016-01-11 18:49:34 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2016-01-12 03:02:35 +0300 |
| commit | 44734f23de2465c3c0d39e4a16df7735b23fd142 (patch) | |
| tree | 9437405c5fff14e2820c0359367386686af80b69 /arch/powerpc | |
| parent | 68adb7bfd66504e97364651fb7dac3f9c8aa8561 (diff) | |
| download | linux-44734f23de2465c3c0d39e4a16df7735b23fd142.tar.xz | |
powerpc/mm: Fix _PAGE_PTE breaking swapoff
Core kernel expects swp_entry_t to consist of only swap type and swap
offset. We should not leak pte bits into swp_entry_t. This breaks
swapoff which use the swap type and offset to build a swp_entry_t and
later compare that to the swp_entry_t obtained from linux page table
pte. Leaking pte bits into swp_entry_t breaks that comparison and
results in us looping in try_to_unuse.
The stack trace can be anywhere below try_to_unuse() in mm/swapfile.c,
since swapoff is circling around and around that function, reading from
each used swap block into a page, then trying to find where that page
belongs, looking at every non-file pte of every mm that ever swapped.
Fixes: 6a119eae942c ("powerpc/mm: Add a _PAGE_PTE bit")
Reported-by: Hugh Dickins <hughd@google.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/include/asm/book3s/64/pgtable.h | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index 03c1a5a21c0c..8e040c42e931 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -158,9 +158,14 @@ static inline void pgd_set(pgd_t *pgdp, unsigned long val) #define __swp_entry(type, offset) ((swp_entry_t) { \ ((type) << _PAGE_BIT_SWAP_TYPE) \ | ((offset) << PTE_RPN_SHIFT) }) - -#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val((pte)) }) -#define __swp_entry_to_pte(x) __pte((x).val) +/* + * swp_entry_t must be independent of pte bits. We build a swp_entry_t from + * swap type and offset we get from swap and convert that to pte to find a + * matching pte in linux page table. + * Clear bits not found in swap entries here. + */ +#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val((pte)) & ~_PAGE_PTE }) +#define __swp_entry_to_pte(x) __pte((x).val | _PAGE_PTE) #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY #define _PAGE_SWP_SOFT_DIRTY (1UL << (SWP_TYPE_BITS + _PAGE_BIT_SWAP_TYPE)) |