Commit a49145ac authored Jul 07, 2020 by George Kennedy Committed by Bartlomiej Zolnierkiewicz Sep 08, 2020

fbmem: add margin check to fb_check_caps()

A fb_ioctl() FBIOPUT_VSCREENINFO call with invalid xres setting
or yres setting in struct fb_var_screeninfo will result in a
KASAN: vmalloc-out-of-bounds failure in bitfill_aligned() as
the margins are being cleared. The margins are cleared in
chunks and if the xres setting or yres setting is a value of
zero upto the chunk size, the failure will occur.

Add a margin check to validate xres and yres settings.

Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Reported-by: <syzbot+e5fd3e65515b48c02a30@syzkaller.appspotmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dhaval Giani <dhaval.giani@oracle.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1594149963-13801-1-git-send-email-george.kennedy@oracle.com

parent 54d04ea8

drivers/video/fbdev/core/fbmem.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1006,6 +1006,10 @@ fb_set_var(struct fb_info info, struct fb_var_screeninfo var)
		return 0;
		}

		/* bitfill_aligned() assumes that it's at least 8x8 */
		if (var->xres < 8 \|\| var->yres < 8)
		return -EINVAL;

		ret = info->fbops->fb_check_var(var, info);

		if (ret)