[PATCH] drm/sysfb: ofdrm: Fix integer overflow in fb_size calculation

[oushixiong1025]

From: Shixiong Ou <oushixiong@xxxxxxxxxx>

The framebuffer size calculation `fb_size = linebytes * height` can
overflow when both values are large (e.g., 46341 * 46341 > INT_MAX).
Since linebytes and height are both int types, the multiplication is
performed as int * int, which results in undefined behavior on overflow.

Use check_mul_overflow() to detect and prevent this overflow, consistent
with the approach used in simpledrm.c and corebootdrm.c.

Signed-off-by: Shixiong Ou <oushixiong@xxxxxxxxxx>
---
 drivers/gpu/drm/sysfb/ofdrm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sysfb/ofdrm.c b/drivers/gpu/drm/sysfb/ofdrm.c
index 819aed466727..a6dc34b9ec0f 100644
--- a/drivers/gpu/drm/sysfb/ofdrm.c
+++ b/drivers/gpu/drm/sysfb/ofdrm.c
@@ -2,6 +2,7 @@
 
 #include <linux/aperture.h>
 #include <linux/of_address.h>
+#include <linux/overflow.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
@@ -913,7 +914,10 @@ static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
 			return ERR_PTR(-EINVAL);
 	}
 
-	fb_size = linebytes * height;
+	if (check_mul_overflow(linebytes, height, &fb_size)) {
+		drm_err(dev, "framebuffer size exceeds maximum\n");
+		return ERR_PTR(-EINVAL);
+	}
 
 	/*
 	 * Try to figure out the address of the framebuffer. Unfortunately, Open
-- 
2.25.1


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