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>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 65cc424359b0..a828c6a276a8 100644
--- 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;