mtd: parsers: ofpart: call of_node_get() for dedicated subpartitions

[ Upstream commit e882626 ]

In order to parse sub-partitions, add_mtd_partitions() calls
parse_mtd_partitions() for all previously found partitions.

Each partition will end up being passed to parse_fixed_partitions(), and
its of_node will be treated as the ofpart_node.

Commit 7cce81d ("mtd: parsers: ofpart: fix OF node refcount leak in
parse_fixed_partitions()") added of_node_put() calls for ofpart_node on
all exit paths.

In the case where the partition passed to parse_fixed_partitions() has a
parent, it is treated as a dedicated partitions node, and of_node_put()
is wrongly called for it, even if of_node_get() was not called
explicitly.

On repeated bind / unbinds of the MTD, the extra of_node_put() ends up
decrementing the refcount down to 0, which should never happen,
resulting in the following error:

OF: ERROR: of_node_release() detected bad of_node_put() on
/soc/spi@80007000/flash@0/partitions/partition@0

Call of_node_get() to balance the call to of_node_put() done for
dedicated partitions nodes.

Fixes: 7cce81d ("mtd: parsers: ofpart: fix OF node refcount leak in parse_fixed_partitions()")
Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Tested-by: Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Demon000

drivers/mtd/parsers/ofpart_core.c

@@ -71,7 +71,7 @@ static int parse_fixed_partitions(struct mtd_info *master,
 			dedicated = false;
 		}
 	} else { /* Partition */
-		ofpart_node = mtd_node;
+		ofpart_node = of_node_get(mtd_node);
 	}
 
 	of_id = of_match_node(parse_ofpart_match_table, ofpart_node);