rbd: prevent bytes transferred overflow

In rbd_obj_read_sync(), verify the number of bytes transferred won't
exceed what can be represented by a size_t before using it to
indicate the number of bytes to copy to the result buffer.

(The real motivation for this is to prepare for the next patch.)

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 09514d9d8a9748d785b3bd2cf6e82d2ca4dd909b..93369a1a08e1a7194f6ee2427f8c6db20fa965d0 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2048,6 +2048,7 @@ static int rbd_obj_read_sync(struct rbd_device *rbd_dev,
        struct ceph_osd_client *osdc;
        struct page **pages = NULL;
        u32 page_count;
+       size_t size;
        int ret;
 
        page_count = (u32) calc_pages_for(offset, length);
@@ -2084,7 +2085,10 @@ static int rbd_obj_read_sync(struct rbd_device *rbd_dev,
        ret = obj_request->result;
        if (ret < 0)
                goto out;
-       ret = ceph_copy_from_page_vector(pages, buf, 0, obj_request->xferred);
+
+       rbd_assert(obj_request->xferred <= (u64) SIZE_MAX);
+       size = (size_t) obj_request->xferred;
+       ret = ceph_copy_from_page_vector(pages, buf, 0, size);
        if (version)
                *version = obj_request->version;
 out: