nvmem: core: Fix cell lookup when no cell is found

If the cell list is not empty and nvmem_find_cell_by_node/name() is
called for a cell that is not present in the list they will return an
invalid pointer instead of NULL. This happen because
list_for_each_entry() stop once it reach the list head again, but as
the list head is not contained in a struct nvmem_cell the iteration
variable then contains an invalid value.

This is easily solved by using a variable to iterate over the list and
one to return the cell found.
Signed-off-by: Alban Bedel <albeu@free.fr>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -525,12 +525,14 @@ static int nvmem_add_cells_from_table(struct nvmem_device *nvmem)
 static struct nvmem_cell *
 nvmem_find_cell_by_name(struct nvmem_device *nvmem, const char *cell_id)
 {
-	struct nvmem_cell *cell = NULL;
+	struct nvmem_cell *iter, *cell = NULL;
 
 	mutex_lock(&nvmem_mutex);
-	list_for_each_entry(cell, &nvmem->cells, node) {
-		if (strcmp(cell_id, cell->name) == 0)
+	list_for_each_entry(iter, &nvmem->cells, node) {
+		if (strcmp(cell_id, iter->name) == 0) {
+			cell = iter;
 			break;
+		}
 	}
 	mutex_unlock(&nvmem_mutex);
 
@@ -994,12 +996,14 @@ nvmem_cell_get_from_lookup(struct device *dev, const char *con_id)
 static struct nvmem_cell *
 nvmem_find_cell_by_node(struct nvmem_device *nvmem, struct device_node *np)
 {
-	struct nvmem_cell *cell = NULL;
+	struct nvmem_cell *iter, *cell = NULL;
 
 	mutex_lock(&nvmem_mutex);
-	list_for_each_entry(cell, &nvmem->cells, node) {
-		if (np == cell->np)
+	list_for_each_entry(iter, &nvmem->cells, node) {
+		if (np == iter->np) {
+			cell = iter;
 			break;
+		}
 	}
 	mutex_unlock(&nvmem_mutex);