libceph: (re)initialize bio_iter on start of message receive

Previously, we were opportunistically initializing the bio_iter if it
appeared to be uninitialized in the middle of the read path.  The problem
is that a sequence like:

 - start reading message
 - initialize bio_iter
 - read half a message
 - messenger fault, reconnect
 - restart reading message
 - ** bio_iter now non-NULL, not reinitialized **
 - read past end of bio, crash

Instead, initialize the bio_iter unconditionally when we allocate/claim
the message for read.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index e65b15d5d8b9..f1bd3bbb0c46 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1872,6 +1872,11 @@ static int read_partial_message(struct ceph_connection *con)
                 else
                         con->in_msg_pos.page_pos = 0;
                 con->in_msg_pos.data_pos = 0;
+
+#ifdef CONFIG_BLOCK
+                if (m->bio)
+                        init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
+#endif
         }
 
         /* front */
@@ -1888,10 +1893,6 @@ static int read_partial_message(struct ceph_connection *con)
                 if (ret <= 0)
                         return ret;
         }
-#ifdef CONFIG_BLOCK
-        if (m->bio && !m->bio_iter)
-                init_bio_iter(m->bio, &m->bio_iter, &m->bio_seg);
-#endif
 
         /* (page) data */
         while (con->in_msg_pos.data_pos < data_len) {
@@ -1902,7 +1903,7 @@ static int read_partial_message(struct ceph_connection *con)
                                 return ret;
 #ifdef CONFIG_BLOCK
                 } else if (m->bio) {
-
+                        BUG_ON(!m->bio_iter);
                         ret = read_partial_message_bio(con,
                                                  &m->bio_iter, &m->bio_seg,
                                                  data_len, do_datacrc);