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From:   Luiz Sampaio <sampaio.ime@gmail.com>
To:     ojeda@kernel.org
Cc:     linux-kernel@vger.kernel.org, Luiz Sampaio <sampaio.ime@gmail.com>
Subject: [PATCH 2/2] auxdisplay: charlcd: checking for pointer reference before dereferencing
Date:   Sun,  7 Nov 2021 12:03:04 -0300
Message-Id: <20211107150304.3253-3-sampaio.ime@gmail.com>
In-Reply-To: <20211107150304.3253-1-sampaio.ime@gmail.com>
References: <20211107150304.3253-1-sampaio.ime@gmail.com>
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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@gmail.com>
---
 drivers/auxdisplay/charlcd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c
index cca3b600c0ba..47363fb2fe94 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 (!lcd->ops->init_display)
+		return -EFAULT;
+
 	ret = lcd->ops->init_display(lcd);
 	if (ret)
 		return ret;
-- 
2.33.1