[PATCH 6.18 339/675] drm/sysfb: Avoid possible truncation with calculating visible size

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Zimmermann <[email protected]>

commit b771974988ec7ce077a7246fa0fa588c246fe581 upstream.

Calculating the visible size of the system framebuffer can result in
truncation of the result. The calculation uses 32-bit arithmetics,
which can overflow if the values for height and stride are large. Fix
the issue by multiplying with mul_u32_u32().

Signed-off-by: Thomas Zimmermann <[email protected]>
Fixes: 32ae90c66fb6 ("drm/sysfb: Add efidrm for EFI displays")
Fixes: a84eb6abe2b6 ("drm/sysfb: Add vesadrm for VESA displays")
Reported-by: Sashiko <[email protected]>
Closes: https://lore.kernel.org/dri-devel/[email protected]/
Cc: Thomas Zimmermann <[email protected]>
Cc: Javier Martinez Canillas <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v6.16+
Reviewed-by: Javier Martinez Canillas <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 drivers/gpu/drm/sysfb/drm_sysfb_screen_info.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/sysfb/drm_sysfb_screen_info.c
+++ b/drivers/gpu/drm/sysfb/drm_sysfb_screen_info.c
@@ -2,6 +2,7 @@
 
 #include <linux/export.h>
 #include <linux/limits.h>
+#include <linux/math64.h>
 #include <linux/minmax.h>
 #include <linux/screen_info.h>
 
@@ -73,7 +74,7 @@ EXPORT_SYMBOL(drm_sysfb_get_stride_si);
 u64 drm_sysfb_get_visible_size_si(struct drm_device *dev, const struct screen_info *si,
 				  unsigned int height, unsigned int stride, u64 size)
 {
-	u64 vsize = height * stride;
+	u64 vsize = mul_u32_u32(height, stride);
 
 	return drm_sysfb_get_validated_size0(dev, "visible size", vsize, size);
 }