nvmem: core: add locking to nvmem_find_cell

Adding entries to nvmem_cells and deleting entries from it is
protected by nvmem_cells_mutex. Therefore this mutex should
also protect iterating over the list.
Signed-off-by: NHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: NSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -287,9 +287,15 @@ static struct nvmem_cell *nvmem_find_cell(const char *cell_id)
 {
 	struct nvmem_cell *p;
 
+	mutex_lock(&nvmem_cells_mutex);
+
 	list_for_each_entry(p, &nvmem_cells, node)
-		if (p && !strcmp(p->name, cell_id))
+		if (p && !strcmp(p->name, cell_id)) {
+			mutex_unlock(&nvmem_cells_mutex);
 			return p;
+		}
+
+	mutex_unlock(&nvmem_cells_mutex);
 
 	return NULL;
 }