badpage: zap print_bad_pte on swap and file

Complete zap_pte_range()'s coverage of bad pagetable entries by calling
print_bad_pte() on a pte_file in a linear vma and on a bad swap entry.
That needs free_swap_and_cache() to tell it, which will also have shown
one of those "swap_free" errors (but with much less information).

Similar checks in fork's copy_one_pte()?  No, that would be more noisy
than helpful: we'll see them when parent and child exec or exit.

Where do_nonlinear_fault() calls print_bad_pte(): omit !VM_CAN_NONLINEAR
case, that could only be a bug in sys_remap_file_pages(), not a bad pte.
VM_FAULT_OOM rather than VM_FAULT_SIGBUS?  Well, okay, that is consistent
with what happens if do_swap_page() operates a bad swap entry; but don't
we have patches to be more careful about killing when VM_FAULT_OOM?

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 11 insertions, 7 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 890095f5f36d..b273cc12b15d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -810,8 +810,12 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
                  */
                 if (unlikely(details))
                         continue;
-                if (!pte_file(ptent))
-                        free_swap_and_cache(pte_to_swp_entry(ptent));
+                if (pte_file(ptent)) {
+                        if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
+                                print_bad_pte(vma, addr, ptent, NULL);
+                } else if
+                  (unlikely(!free_swap_and_cache(pte_to_swp_entry(ptent))))
+                        print_bad_pte(vma, addr, ptent, NULL);
                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
         } while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));
 
@@ -2707,8 +2711,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
                 return 0;
 
-        if (unlikely(!(vma->vm_flags & VM_NONLINEAR) ||
-                        !(vma->vm_flags & VM_CAN_NONLINEAR))) {
+        if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
                 /*
                  * Page table corrupted: show pte and kill process.
                  */
diff --git a/mm/swapfile.c b/mm/swapfile.c
index d00523601913..f28745855772 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -571,13 +571,13 @@ int try_to_free_swap(struct page *page)
  * Free the swap entry like above, but also try to
  * free the page cache entry if it is the last user.
  */
-void free_swap_and_cache(swp_entry_t entry)
+int free_swap_and_cache(swp_entry_t entry)
 {
-        struct swap_info_struct * p;
+        struct swap_info_struct *p;
         struct page *page = NULL;
 
         if (is_migration_entry(entry))
-                return;
+                return 1;
 
         p = swap_info_get(entry);
         if (p) {
@@ -603,6 +603,7 @@ void free_swap_and_cache(swp_entry_t entry)
                 unlock_page(page);
                 page_cache_release(page);
         }
+        return p != NULL;
 }
 
 #ifdef CONFIG_HIBERNATION