From: Lee Jones <lee.jones@linaro.org>
Date: Mon, 21 Oct 2019 09:16:34 +0000 (+0100)
Subject: mfd: mfd-core: Protect against NULL call-back function pointer
X-Git-Tag: v5.5-rc1~95^2~13
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=b195e101580db390f50b0d587b7f66f241d2bc88;p=linux.git

mfd: mfd-core: Protect against NULL call-back function pointer

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>
---

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);