[PATCH] swsusp: prevent possible image corruption on resume

The function free_pagedir() used by swsusp for freeing its internal data
structures clears the PG_nosave and PG_nosave_free flags for each page
being freed.

However, during resume PG_nosave_free set means that the page in
question is "unsafe" (ie.  it will be overwritten in the process of
restoring the saved system state from the image), so it should not be
used for the image data.

Therefore free_pagedir() should not clear PG_nosave_free if it's called
during resume (otherwise "unsafe" pages freed by it may be used for
storing the image data and the data may get corrupted later on).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index c5863d02c89efc08ef430752bb062f0aafcb4bc7..3eeedbb13b7864d525c6740a99156b433e3b6a51 100644 (file)
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -240,14 +240,15 @@ static void copy_data_pages(struct pbe *pblist)
  *     free_pagedir - free pages allocated with alloc_pagedir()
  */
 
-static void free_pagedir(struct pbe *pblist)
+static void free_pagedir(struct pbe *pblist, int clear_nosave_free)
 {
        struct pbe *pbe;
 
        while (pblist) {
                pbe = (pblist + PB_PAGE_SKIP)->next;
                ClearPageNosave(virt_to_page(pblist));
-               ClearPageNosaveFree(virt_to_page(pblist));
+               if (clear_nosave_free)
+                       ClearPageNosaveFree(virt_to_page(pblist));
                free_page((unsigned long)pblist);
                pblist = pbe;
        }
@@ -389,7 +390,7 @@ struct pbe *alloc_pagedir(unsigned int nr_pages, gfp_t gfp_mask, int safe_needed
                pbe->next = alloc_image_page(gfp_mask, safe_needed);
        }
        if (!pbe) { /* get_zeroed_page() failed */
-               free_pagedir(pblist);
+               free_pagedir(pblist, 1);
                pblist = NULL;
         } else
                create_pbe_list(pblist, nr_pages);
@@ -736,7 +737,7 @@ static int create_image(struct snapshot_handle *handle)
                pblist = alloc_pagedir(nr_copy_pages, GFP_ATOMIC, 1);
                if (pblist)
                        copy_page_backup_list(pblist, p);
-               free_pagedir(p);
+               free_pagedir(p, 0);
                if (!pblist)
                        error = -ENOMEM;
        }