Patch "fbmon: prevent division by zero in fb_videomode_from_videomode()" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    fbmon: prevent division by zero in fb_videomode_from_videomode()

to the 4.19-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:
     fbmon-prevent-division-by-zero-in-fb_videomode_from_.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 57e1559fc9b1cb088aab91d20fe83c73389041c0
Author: Roman Smirnov <r.smirnov@xxxxxx>
Date:   Tue Mar 19 11:13:44 2024 +0300

    fbmon: prevent division by zero in fb_videomode_from_videomode()
    
    [ Upstream commit c2d953276b8b27459baed1277a4fdd5dd9bd4126 ]
    
    The expression htotal * vtotal can have a zero value on
    overflow. It is necessary to prevent division by zero like in
    fb_var_to_videomode().
    
    Found by Linux Verification Center (linuxtesting.org) with Svace.
    
    Signed-off-by: Roman Smirnov <r.smirnov@xxxxxx>
    Reviewed-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
    Signed-off-by: Helge Deller <deller@xxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/video/fbdev/core/fbmon.c b/drivers/video/fbdev/core/fbmon.c
index 8607439d69328..e4040fb860bbc 100644
--- a/drivers/video/fbdev/core/fbmon.c
+++ b/drivers/video/fbdev/core/fbmon.c
@@ -1309,7 +1309,7 @@ int fb_get_mode(int flags, u32 val, struct fb_var_screeninfo *var, struct fb_inf
 int fb_videomode_from_videomode(const struct videomode *vm,
 				struct fb_videomode *fbmode)
 {
-	unsigned int htotal, vtotal;
+	unsigned int htotal, vtotal, total;
 
 	fbmode->xres = vm->hactive;
 	fbmode->left_margin = vm->hback_porch;
@@ -1342,8 +1342,9 @@ int fb_videomode_from_videomode(const struct videomode *vm,
 	vtotal = vm->vactive + vm->vfront_porch + vm->vback_porch +
 		 vm->vsync_len;
 	/* prevent division by zero */
-	if (htotal && vtotal) {
-		fbmode->refresh = vm->pixelclock / (htotal * vtotal);
+	total = htotal * vtotal;
+	if (total) {
+		fbmode->refresh = vm->pixelclock / total;
 	/* a mode must have htotal and vtotal != 0 or it is invalid */
 	} else {
 		fbmode->refresh = 0;