[PATCH 3.13 172/187] libceph: set last_piece in ceph_msg_data_pages_cursor_init() correctly

Kamal Mostafa
2014-09-15T22:35:57Z

From: Ilya Dryomov <ilya.dryomov@inktank.com>

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@snap
rbd snap protect foo@snap
rbd clone foo@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@inktank.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Kamal Mostafa <kamal@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