rbd: return an error when an invalid header is read

This protects against opening future rbd images that have incompatible format changes.

Signed-off-by: Josh Durgin <josh.durgin@dreamhost.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 65cc424..a828c6a 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -461,6 +461,10 @@ static int rbd_header_from_disk(struct rbd_image_header *header,
        u32 snap_count = le32_to_cpu(ondisk->snap_count);
        int ret = -ENOMEM;
 
+       if (memcmp(ondisk, RBD_HEADER_TEXT, sizeof(RBD_HEADER_TEXT))) {
+               return -ENXIO;
+       }
+
        init_rwsem(&header->snap_rwsem);
        header->snap_names_len = le64_to_cpu(ondisk->snap_names_len);
        header->snapc = kmalloc(sizeof(struct ceph_snap_context) +
@@ -1610,8 +1614,13 @@ static int rbd_read_header(struct rbd_device *rbd_dev,
                        goto out_dh;
 
                rc = rbd_header_from_disk(header, dh, snap_count, GFP_KERNEL);
-               if (rc < 0)
+               if (rc < 0) {
+                       if (rc == -ENXIO) {
+                               pr_warning("unrecognized header format"
+                                          " for image %s", rbd_dev->obj);
+                       }
                        goto out_dh;
+               }
 
                if (snap_count != header->total_snaps) {
                        snap_count = header->total_snaps;