This is a note to let you know that I've just added the patch titled auxdisplay: charlcd: checking for pointer reference before dereferencing to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: auxdisplay-charlcd-checking-for-pointer-reference-be.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit b637f956500cf4fce047ab5fe998fe4c6d84c2be Author: Luiz Sampaio <sampaio.ime@xxxxxxxxx> Date: Tue Nov 9 19:07:32 2021 -0300 auxdisplay: charlcd: checking for pointer reference before dereferencing [ 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@xxxxxxxxx> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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;