linux-kernel - [ 143/171] libceph: (re)initialize bio

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Date:	Wed, 21 Nov 2012 16:41:29 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Sage Weil <sage@...tank.com>,
	Alex Elder <elder@...tank.com>,
	Yehuda Sadeh <yehuda@...tank.com>
Subject: [ 143/171] libceph: (re)initialize bio_iter on start of message receive

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sage Weil <sage@...tank.com>

(cherry picked from commit a4107026976f06c9a6ce8cc84a763564ee39d901)

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@...tank.com>
Reviewed-by: Alex Elder <elder@...tank.com>
Reviewed-by: Yehuda Sadeh <yehuda@...tank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ceph/messenger.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1872,6 +1872,11 @@ static int read_partial_message(struct c
 		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 c
 		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 c
 				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);


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