pnfs/blocklayout: off by one in bl_map_stripe()

BugLink: https://bugs.launchpad.net/bugs/1792419

commit 0914bb96 upstream.

"dev->nr_children" is the number of children which were parsed
successfully in bl_parse_stripe().  It could be all of them and then, in
that case, it is equal to v->stripe.volumes_count.  Either way, the >
should be >= so that we don't go beyond the end of what we're supposed
to.

Fixes: 5c83746a ("pnfs/blocklayout: in-kernel GETDEVICEINFO XDR parsing")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org # 3.17+
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

fs/nfs/blocklayout/dev.c

@@ -162,7 +162,7 @@ static bool bl_map_stripe(struct pnfs_block_dev *dev, u64 offset,
 	chunk = div_u64(offset, dev->chunk_size);
 	div_u64_rem(chunk, dev->nr_children, &chunk_idx);
 
-	if (chunk_idx > dev->nr_children) {
+	if (chunk_idx >= dev->nr_children) {
 		dprintk("%s: invalid chunk idx %d (%lld/%lld)\n",
 			__func__, chunk_idx, offset, dev->chunk_size);
 		/* error, should not happen */