linux-kernel - [PATCH 5.15 53/72] auxdisplay: charlcd: checking for pointer reference before dereferencing

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Date:   Mon, 10 Jan 2022 08:23:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Luiz Sampaio <sampaio.ime@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 53/72] auxdisplay: charlcd: checking for pointer reference before dereferencing

From: Luiz Sampaio <sampaio.ime@...il.com>

[ Upstream commit 4daa9ff89ef27be43c15995412d6aee393a78200 ]

Check if the pointer lcd->ops->init_display exists before dereferencing it.
If a driver called charlcd_init() without defining the ops, this would
return segmentation fault, as happened to me when implementing a charlcd
driver.  Checking the pointer before dereferencing protects from
segmentation fault.

Signed-off-by: Luiz Sampaio <sampaio.ime@...il.com>
Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/auxdisplay/charlcd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index 304accde365c8..6c010d4efa4ae 100644
--- a/drivers/auxdisplay/charlcd.c
+++ b/drivers/auxdisplay/charlcd.c
@@ -578,6 +578,9 @@ static int charlcd_init(struct charlcd *lcd)
 	 * Since charlcd_init_display() needs to write data, we have to
 	 * enable mark the LCD initialized just before.
 	 */
+	if (WARN_ON(!lcd->ops->init_display))
+		return -EINVAL;
+
 	ret = lcd->ops->init_display(lcd);
 	if (ret)
 		return ret;
-- 
2.34.1