[3.13.y.z extended stable] Patch "libceph: set last_piece in ceph_msg_data_pages_cursor_init() correctly" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    libceph: set last_piece in ceph_msg_data_pages_cursor_init() correctly

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 0243f5c9d2bb5f8c578e46316f733721cf141c9f Mon Sep 17 00:00:00 2001
From: Ilya Dryomov <ilya.dryomov at inktank.com>
Date: Fri, 8 Aug 2014 12:43:39 +0400
Subject: libceph: set last_piece in ceph_msg_data_pages_cursor_init()
 correctly

commit 5f740d7e1531099b888410e6bab13f68da9b1a4d upstream.

Determining ->last_piece based on the value of ->page_offset + length
is incorrect because length here is the length of the entire message.
->last_piece set to false even if page array data item length is <=
PAGE_SIZE, which results in invalid length passed to
ceph_tcp_{send,recv}page() and causes various asserts to fire.

    # cat pages-cursor-init.sh
    #!/bin/bash
    rbd create --size 10 --image-format 2 foo
    FOO_DEV=$(rbd map foo)
    dd if=/dev/urandom of=$FOO_DEV bs=1M &>/dev/null
    rbd snap create foo at snap
    rbd snap protect foo at snap
    rbd clone foo at snap bar
    # rbd_resize calls librbd rbd_resize(), size is in bytes
    ./rbd_resize bar $(((4 << 20) + 512))
    rbd resize --size 10 bar
    BAR_DEV=$(rbd map bar)
    # trigger a 512-byte copyup -- 512-byte page array data item
    dd if=/dev/urandom of=$BAR_DEV bs=1M count=1 seek=5

The problem exists only in ceph_msg_data_pages_cursor_init(),
ceph_msg_data_pages_advance() does the right thing.  The size_t cast is
unnecessary.

Signed-off-by: Ilya Dryomov <ilya.dryomov at inktank.com>
Reviewed-by: Sage Weil <sage at redhat.com>
Reviewed-by: Alex Elder <elder at linaro.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/ceph/messenger.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index ce83d07..94e21b9 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -904,7 +904,7 @@ static void ceph_msg_data_pages_cursor_init(struct ceph_msg_data_cursor *cursor,
 	BUG_ON(page_count > (int)USHRT_MAX);
 	cursor->page_count = (unsigned short)page_count;
 	BUG_ON(length > SIZE_MAX - cursor->page_offset);
-	cursor->last_piece = (size_t)cursor->page_offset + length <= PAGE_SIZE;
+	cursor->last_piece = cursor->page_offset + cursor->resid <= PAGE_SIZE;
 }

 static struct page *
--
1.9.1