From patchwork Mon Aug 31 10:37:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 293268 From: Tetsuo Handa Date: Mon, 31 Aug 2020 10:37:00 +0000 Subject: [PATCH v2 (resend)] video: fbdev: fix OOB read in vga_8planes_imageblit() Message-Id: <90b55ec3-d5b0-3307-9f7c-7ff5c5fd6ad3@i-love.sakura.ne.jp> List-Id: References: <11ad8786-e407-3289-8bd9-2745c4834718@i-love.sakura.ne.jp> In-Reply-To: <11ad8786-e407-3289-8bd9-2745c4834718@i-love.sakura.ne.jp> MIME-Version: 1.0 To: Greg Kroah-Hartman Cc: Linux Fbdev development list , DRI , Bartlomiej Zolnierkiewicz syzbot is reporting OOB read at vga_8planes_imageblit() [1], for "cdat[y] >> 4" can become a negative value due to "const char *cdat". [1] https://syzkaller.appspot.com/bug?id 7a0da1557dcd1989e00cb3692b26d4173b4132 Reported-by: syzbot Signed-off-by: Tetsuo Handa --- drivers/video/fbdev/vga16fb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c index a20eeb8308ff..578d3541e3d6 100644 --- a/drivers/video/fbdev/vga16fb.c +++ b/drivers/video/fbdev/vga16fb.c @@ -1121,7 +1121,7 @@ static void vga_8planes_imageblit(struct fb_info *info, const struct fb_image *i char oldop = setop(0); char oldsr = setsr(0); char oldmask = selectmask(); - const char *cdat = image->data; + const unsigned char *cdat = image->data; u32 dx = image->dx; char __iomem *where; int y;