md: check that internal bitmap does not overlap other data

We current completely trust user-space to set up metadata describing an
consistant array.  In particlar, that the metadata, data, and bitmap do not
overlap.

But userspace can be buggy, and it is better to report an error than corrupt
data.  So put in some appropriate checks.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 33 insertions, 2 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 9620d452d030..ae94f3beb5fc 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -268,6 +268,31 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
                         if (page->index == bitmap->file_pages-1)
                                 size = roundup(bitmap->last_page_size,
                                                bdev_hardsect_size(rdev->bdev));
+                        /* Just make sure we aren't corrupting data or
+                         * metadata
+                         */
+                        if (bitmap->offset < 0) {
+                                /* DATA  BITMAP METADATA  */
+                                if (bitmap->offset
+                                    + page->index * (PAGE_SIZE/512)
+                                    + size/512 > 0)
+                                        /* bitmap runs in to metadata */
+                                        return -EINVAL;
+                                if (rdev->data_offset + mddev->size*2
+                                    > rdev->sb_offset*2 + bitmap->offset)
+                                        /* data runs in to bitmap */
+                                        return -EINVAL;
+                        } else if (rdev->sb_offset*2 < rdev->data_offset) {
+                                /* METADATA BITMAP DATA */
+                                if (rdev->sb_offset*2
+                                    + bitmap->offset
+                                    + page->index*(PAGE_SIZE/512) + size/512
+                                    > rdev->data_offset)
+                                        /* bitmap runs in to data */
+                                        return -EINVAL;
+                        } else {
+                                /* DATA METADATA BITMAP - no problems */
+                        }
                         md_super_write(mddev, rdev,
                                        (rdev->sb_offset<<1) + bitmap->offset
                                        + page->index * (PAGE_SIZE/512),
@@ -287,8 +312,14 @@ static int write_page(struct bitmap *bitmap, struct page *page, int wait)
 {
         struct buffer_head *bh;
 
-        if (bitmap->file == NULL)
-                return write_sb_page(bitmap, page, wait);
+        if (bitmap->file == NULL) {
+                switch (write_sb_page(bitmap, page, wait)) {
+                case -EINVAL:
+                        bitmap->flags |= BITMAP_WRITE_ERROR;
+                        return -EIO;
+                }
+                return 0;
+        }
 
         bh = page_buffers(page);