From b195e101580db390f50b0d587b7f66f241d2bc88 Mon Sep 17 00:00:00 2001
From: Lee Jones <lee.jones@linaro.org>
Date: Mon, 21 Oct 2019 10:16:34 +0100
Subject: [PATCH] mfd: mfd-core: Protect against NULL call-back function pointer
Git-commit: b195e101580db390f50b0d587b7f66f241d2bc88
Patch-mainline: v5.5-rc1
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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);
-- 
2.16.4