fbdev: Fixing arbitrary kernel leak in case FBIOGETCMAP_SPARC in sbusfb_ioctl_helper().

petermalone · bzolnier · commit 250c6c49e3b6 · 2018-03-07T14:00:34.000+01:00
Fixing arbitrary kernel leak in case FBIOGETCMAP_SPARC in sbusfb_ioctl_helper(). 'index' is defined as an int in sbusfb_ioctl_helper(). We retrieve this from the user: if (get_user(index, &c->index) || __get_user(count, &c->count) || __get_user(ured, &c->red) || __get_user(ugreen, &c->green) || __get_user(ublue, &c->blue)) return -EFAULT; and then we use 'index' in the following way: red = cmap->red[index + i] >> 8; green = cmap->green[index + i] >> 8; blue = cmap->blue[index + i] >> 8; This is a classic information leak vulnerability. 'index' should be an unsigned int, given its usage above. This patch is straight-forward; it changes 'index' to unsigned int in two switch-cases: FBIOGETCMAP_SPARC && FBIOPUTCMAP_SPARC. This patch fixes CVE-2018-6412. Signed-off-by: Peter Malone <peter.malone@gmail.com> Acked-by: Mathieu Malaterre <malat@debian.org> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
@@ -122,7 +122,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
 		unsigned char __user *ured;
 		unsigned char __user *ugreen;
 		unsigned char __user *ublue;
-		int index, count, i;
+		unsigned int index, count, i;
 
 		if (get_user(index, &c->index) ||
 		    __get_user(count, &c->count) ||
@@ -161,7 +161,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
 		unsigned char __user *ugreen;
 		unsigned char __user *ublue;
 		struct fb_cmap *cmap = &info->cmap;
-		int index, count, i;
+		unsigned int index, count, i;
 		u8 red, green, blue;
 
 		if (get_user(index, &c->index) ||
