[PATCH AUTOSEL 6.1 23/28] rtc: msc313: Fix function prototype mismatch in msc313_rtc_probe()

[Sasha Levin]

From: Kees Cook <keescook at chromium.org>

[ Upstream commit 21b8a1dd56a163825e5749b303858fb902ebf198 ]

With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
indirect call targets are validated against the expected function
pointer prototype to make sure the call target is valid to help mitigate
ROP attacks. If they are not identical, there is a failure at run time,
which manifests as either a kernel panic or thread getting killed.

msc313_rtc_probe() was passing clk_disable_unprepare() directly, which
did not have matching prototypes for devm_add_action_or_reset()'s
callback argument. Refactor to use devm_clk_get_enabled() instead.

This was found as a result of Clang's new -Wcast-function-type-strict
flag, which is more sensitive than the simpler -Wcast-function-type,
which only checks for type width mismatches.

Reported-by: kernel test robot <lkp at intel.com>
Link: https://lore.kernel.org/lkml/202211041527.HD8TLSE1-lkp@intel.com
Suggested-by: Christophe JAILLET <christophe.jaillet at wanadoo.fr>
Cc: Daniel Palmer <daniel at thingy.jp>
Cc: Romain Perier <romain.perier at gmail.com>
Cc: Alessandro Zummo <a.zummo at towertech.it>
Cc: Alexandre Belloni <alexandre.belloni at bootlin.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-rtc at vger.kernel.org
Signed-off-by: Kees Cook <keescook at chromium.org>
Reviewed-by: Daniel Palmer <daniel at thingy.jp>
Tested-by: Daniel Palmer <daniel at thingy.jp>
Link: https://lore.kernel.org/r/20221202184525.gonna.423-kees@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni at bootlin.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/rtc/rtc-msc313.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/drivers/rtc/rtc-msc313.c b/drivers/rtc/rtc-msc313.c
index f3fde013c4b8..8d7737e0e2e0 100644
--- a/drivers/rtc/rtc-msc313.c
+++ b/drivers/rtc/rtc-msc313.c
@@ -212,22 +212,12 @@ static int msc313_rtc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	clk = devm_clk_get(dev, NULL);
+	clk = devm_clk_get_enabled(dev, NULL);
 	if (IS_ERR(clk)) {
 		dev_err(dev, "No input reference clock\n");
 		return PTR_ERR(clk);
 	}
 
-	ret = clk_prepare_enable(clk);
-	if (ret) {
-		dev_err(dev, "Failed to enable the reference clock, %d\n", ret);
-		return ret;
-	}
-
-	ret = devm_add_action_or_reset(dev, (void (*) (void *))clk_disable_unprepare, clk);
-	if (ret)
-		return ret;
-
 	rate = clk_get_rate(clk);
 	writew(rate & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_L);
 	writew((rate >> 16) & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_H);
-- 
2.35.1