From: Dan Rosenberg <drosenberg@vsecurity.com>
Date: Wed, 22 Sep 2010 20:05:09 +0000 (-0700)
Subject: drivers/video/sis/sis_main.c: prevent reading uninitialized stack memory
X-Git-Tag: firefly_0821_release~10186^2~902
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e286d83959320fcf7eadfc81aeceb6e1a81667c9;p=firefly-linux-kernel-4.4.55.git

drivers/video/sis/sis_main.c: prevent reading uninitialized stack memory

commit fd02db9de73faebc51240619c7c7f99bee9f65c7 upstream.

The FBIOGET_VBLANK device ioctl allows unprivileged users to read 16 bytes
of uninitialized stack memory, because the "reserved" member of the
fb_vblank struct declared on the stack is not altered or zeroed before
being copied back to the user.  This patch takes care of it.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Cc: Thomas Winischhofer <thomas@winischhofer.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/drivers/video/sis/sis_main.c b/drivers/video/sis/sis_main.c
index a4e05e4d7501..e1836d7140a8 100644
--- a/drivers/video/sis/sis_main.c
+++ b/drivers/video/sis/sis_main.c
@@ -1701,6 +1701,9 @@ static int	sisfb_ioctl(struct fb_info *info, unsigned int cmd,
 		break;
 
 	   case FBIOGET_VBLANK:
+
+		memset(&sisvbblank, 0, sizeof(struct fb_vblank));
+
 		sisvbblank.count = 0;
 		sisvbblank.flags = sisfb_setupvbblankflags(ivideo, &sisvbblank.vcount, &sisvbblank.hcount);