[PATCH] mm: parisc pte atomicity
There's a worrying function translation_exists in parisc cacheflush.h,
unaffected by split ptlock since flush_dcache_page is using it on some other
mm, without any relevant lock. Oh well, make it a slightly more robust by
factoring the pfn check within it. And it looked liable to confuse a
camouflaged swap or file entry with a good pte: fix that too.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-parisc/cacheflush.h b/include/asm-parisc/cacheflush.h
index aa592d8..1bc3c83 100644
--- a/include/asm-parisc/cacheflush.h
+++ b/include/asm-parisc/cacheflush.h
@@ -100,30 +100,34 @@
/* Simple function to work out if we have an existing address translation
* for a user space vma. */
-static inline pte_t *__translation_exists(struct mm_struct *mm,
- unsigned long addr)
+static inline int translation_exists(struct vm_area_struct *vma,
+ unsigned long addr, unsigned long pfn)
{
- pgd_t *pgd = pgd_offset(mm, addr);
+ pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
pmd_t *pmd;
- pte_t *pte;
+ pte_t pte;
if(pgd_none(*pgd))
- return NULL;
+ return 0;
pmd = pmd_offset(pgd, addr);
if(pmd_none(*pmd) || pmd_bad(*pmd))
- return NULL;
+ return 0;
- pte = pte_offset_map(pmd, addr);
+ /* We cannot take the pte lock here: flush_cache_page is usually
+ * called with pte lock already held. Whereas flush_dcache_page
+ * takes flush_dcache_mmap_lock, which is lower in the hierarchy:
+ * the vma itself is secure, but the pte might come or go racily.
+ */
+ pte = *pte_offset_map(pmd, addr);
+ /* But pte_unmap() does nothing on this architecture */
- /* The PA flush mappings show up as pte_none, but they're
- * valid none the less */
- if(pte_none(*pte) && ((pte_val(*pte) & _PAGE_FLUSH) == 0))
- return NULL;
- return pte;
+ /* Filter out coincidental file entries and swap entries */
+ if (!(pte_val(pte) & (_PAGE_FLUSH|_PAGE_PRESENT)))
+ return 0;
+
+ return pte_pfn(pte) == pfn;
}
-#define translation_exists(vma, addr) __translation_exists((vma)->vm_mm, addr)
-
/* Private function to flush a page from the cache of a non-current
* process. cr25 contains the Page Directory of the current user
@@ -175,9 +179,8 @@
{
BUG_ON(!vma->vm_mm->context);
- if(likely(translation_exists(vma, vmaddr)))
+ if (likely(translation_exists(vma, vmaddr, pfn)))
__flush_cache_page(vma, vmaddr);
}
#endif
-