[PATCH 2/4] drm/log: Fix division by zero when scale module parameter is 0

[oushixiong1025]

From: Shixiong Ou <oushixiong@xxxxxxxxxx>

The scale module parameter can be set to 0 via kernel command line or
sysfs. When scale is 0, scaled_font_h and scaled_font_w become 0,
causing a division by zero in the rows/columns calculation.

Add a custom param_ops setter to clamp scale to a minimum of 1 at the
source, ensuring scale is always valid for all users.

Signed-off-by: Shixiong Ou <oushixiong@xxxxxxxxxx>
---
 drivers/gpu/drm/clients/drm_log.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/clients/drm_log.c b/drivers/gpu/drm/clients/drm_log.c
index 294b3be1a6b3..a04f651e8265 100644
--- a/drivers/gpu/drm/clients/drm_log.c
+++ b/drivers/gpu/drm/clients/drm_log.c
@@ -26,7 +26,27 @@ MODULE_DESCRIPTION("DRM boot logger");
 MODULE_LICENSE("GPL");
 
 static unsigned int scale = 1;
-module_param(scale, uint, 0444);
+
+static int drm_log_scale_set(const char *val, const struct kernel_param *kp)
+{
+	int ret;
+
+	ret = param_set_uint(val, kp);
+	if (ret)
+		return ret;
+
+	if (scale < 1)
+		scale = 1;
+
+	return 0;
+}
+
+static const struct kernel_param_ops drm_log_scale_ops = {
+	.set	= drm_log_scale_set,
+	.get	= param_get_uint,
+};
+
+module_param_cb(scale, &drm_log_scale_ops, &scale, 0444);
 MODULE_PARM_DESC(scale, "Integer scaling factor for drm_log, default is 1");
 
 /**
-- 
2.25.1


No virus found
		Checked by Hillstone Network AntiVirus