[PATCH v4 05/10] mfd: mfd-core: Protect against NULL call-back function pointer

Lee Jones
2019-11-01T07:46:41Z

If a child device calls mfd_cell_{en,dis}able() without an appropriate
call-back being set, we are likely to encounter a panic. Avoid this
by adding suitable checking.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
---
drivers/mfd/mfd-core.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
index 23276a80e3b4..96d02b6f06fd 100644
--- a/drivers/mfd/mfd-core.c
+++ b/drivers/mfd/mfd-core.c
@@ -28,6 +28,11 @@ int mfd_cell_enable(struct platform_device *pdev)
const struct mfd_cell *cell = mfd_get_cell(pdev);
int err = 0;

+ if (!cell->enable) {
+ dev_dbg(&pdev->dev, "No .enable() call-back registered\n");
+ return 0;
+ }
+
/* only call enable hook if the cell wasn't previously enabled */
if (atomic_inc_return(cell->usage_count) == 1)
err = cell->enable(pdev);
@@ -45,6 +50,11 @@ int mfd_cell_disable(struct platform_device *pdev)
const struct mfd_cell *cell = mfd_get_cell(pdev);
int err = 0;

+ if (!cell->disable) {
+ dev_dbg(&pdev->dev, "No .disable() call-back registered\n");
+ return 0;
+ }
+
/* only disable if no other clients are using it */
if (atomic_dec_return(cell->usage_count) == 0)
err = cell->disable(pdev);