[PATCH 2/2] nvmem: core: fix use-after-free bugs in error paths

[srini]

From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>

Fix several instances of error paths in which we call
__nvmem_device_put() - which may end up freeing the underlying memory
and other resources - and then keep on using the nvmem structure. Always
put the reference to the nvmem device as the last step before returning
the error code.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 7ae6478b304b ("nvmem: core: rework nvmem cell instance creation")
Fixes: e888d445ac33 ("nvmem: resolve cells from DT at registration time")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
Signed-off-by: Srinivas Kandagatla <srini@xxxxxxxxxx>
---
 drivers/nvmem/core.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 311cb2e5a5c0..e871181751f3 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1468,18 +1468,16 @@ struct nvmem_cell *of_nvmem_cell_get(struct device_node *np, const char *id)
 	cell_entry = nvmem_find_cell_entry_by_node(nvmem, cell_np);
 	of_node_put(cell_np);
 	if (!cell_entry) {
-		__nvmem_device_put(nvmem);
 		nvmem_layout_module_put(nvmem);
-		if (nvmem->layout)
-			return ERR_PTR(-EPROBE_DEFER);
-		else
-			return ERR_PTR(-ENOENT);
+		ret = nvmem->layout ? -EPROBE_DEFER : -ENOENT;
+		__nvmem_device_put(nvmem);
+		return ERR_PTR(ret);
 	}
 
 	cell = nvmem_create_cell(cell_entry, id, cell_index);
 	if (IS_ERR(cell)) {
-		__nvmem_device_put(nvmem);
 		nvmem_layout_module_put(nvmem);
+		__nvmem_device_put(nvmem);
 	}
 
 	return cell;
@@ -1593,8 +1591,8 @@ void nvmem_cell_put(struct nvmem_cell *cell)
 		kfree_const(cell->id);
 
 	kfree(cell);
-	__nvmem_device_put(nvmem);
 	nvmem_layout_module_put(nvmem);
+	__nvmem_device_put(nvmem);
 }
 EXPORT_SYMBOL_GPL(nvmem_cell_put);
 
-- 
2.53.0