net: fix rds_iovec page count overflow

commit 1b1f693d7ad6d193862dcb1118540a030c5e761f upstream.

As reported by Thomas Pollet, the rdma page counting can overflow.  We
get the rdma sizes in 64-bit unsigned entities, but then limit it to
UINT_MAX bytes and shift them down to pages (so with a possible "+1" for
an unaligned address).

So each individual page count fits comfortably in an 'unsigned int' (not
even close to overflowing into signed), but as they are added up, they
might end up resulting in a signed return value. Which would be wrong.

Catch the case of tot_pages turning negative, and return the appropriate
error code.

Reported-by: Thomas Pollet <thomas.pollet@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 1fa0f4b9fac3e306d6d5751d58d4c7fda360f72b..4810a25a53c7264b028991ef8b026b840ae75c8a 100644 (file)
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -497,6 +497,14 @@ static struct rds_rdma_op *rds_rdma_prepare(struct rds_sock *rs,
 
                max_pages = max(nr, max_pages);
                nr_pages += nr;
+
+               /*
+                * nr_pages for one entry is limited to (UINT_MAX>>PAGE_SHIFT)+1,
+                * so tot_pages cannot overflow without first going negative.
+                */
+               if ((int)nr_pages < 0)
+                       ret = -EINVAL;
+                       goto out;
        }
 
        pages = kcalloc(max_pages, sizeof(struct page *), GFP_KERNEL);