linux-kernel - [PATCH] drivers/video/sis/sis_main.c: prevent reading uninitialized stack memory

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Date:	Wed, 15 Sep 2010 17:43:53 -0400
From:	Dan Rosenberg <drosenberg@...curity.com>
To:	thomas@...ischhofer.net
Cc:	linux-kernel@...r.kernel.org, security@...nel.org,
	stable@...nel.org
Subject: [PATCH] drivers/video/sis/sis_main.c: prevent reading
 uninitialized stack memory

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@...il.com>

--- linux-2.6.35.4.orig/drivers/video/sis/sis_main.c	2010-08-26 19:47:12.000000000 -0400
+++ linux-2.6.35.4/drivers/video/sis/sis_main.c	2010-09-15 11:52:41.437375730 -0400
@@ -1701,6 +1701,9 @@ static int	sisfb_ioctl(struct fb_info *i
 		break;
 
 	   case FBIOGET_VBLANK:
+
+		memset(&sisvbblank, 0, sizeof(struct fb_vblank));
+
 		sisvbblank.count = 0;
 		sisvbblank.flags = sisfb_setupvbblankflags(ivideo, &sisvbblank.vcount, &sisvbblank.hcount);
 




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