From 3b82a4db8eaccce735dffd50b4d4e1578099b8e8 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Wed, 21 Mar 2018 16:45:53 +0100
Subject: [PATCH] drm: udl: Properly check framebuffer mmap offsets
Git-commit: 3b82a4db8eaccce735dffd50b4d4e1578099b8e8
Patch-mainline: v4.16-rc7
References: bsc#1051510, CVE-2018-8781, bsc#1090643 

The memmap options sent to the udl framebuffer driver were not being
checked for all sets of possible crazy values.  Fix this up by properly
bounding the allowed values.

Reported-by: Eyal Itkin <eyalit@checkpoint.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180321154553.GA18454@kroah.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/udl/udl_fb.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/udl/udl_fb.c
+++ b/drivers/gpu/drm/udl/udl_fb.c
@@ -159,10 +159,15 @@ static int udl_fb_mmap(struct fb_info *i
 {
 	unsigned long start = vma->vm_start;
 	unsigned long size = vma->vm_end - vma->vm_start;
-	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
+	unsigned long offset;
 	unsigned long page, pos;
 
-	if (offset + size > info->fix.smem_len)
+	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT))
+		return -EINVAL;
+
+	offset = vma->vm_pgoff << PAGE_SHIFT;
+
+	if (offset > info->fix.smem_len || size > info->fix.smem_len - offset)
 		return -EINVAL;
 
 	pos = (unsigned long)info->fix.smem_start + offset;