linux-kernel - [34-longterm 133/260] drivers/video/sis/sis_main.c: prevent reading uninitialized stack memory

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Date:	Sun,  2 Jan 2011 02:17:09 -0500
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Dan Rosenberg <drosenberg@...curity.com>,
	Dan Rosenberg <dan.j.rosenberg@...il.com>,
	Thomas Winischhofer <thomas@...ischhofer.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 133/260] drivers/video/sis/sis_main.c: prevent reading uninitialized stack memory

From: Dan Rosenberg <drosenberg@...curity.com>

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@...il.com>
Cc: Thomas Winischhofer <thomas@...ischhofer.net>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 drivers/video/sis/sis_main.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/video/sis/sis_main.c b/drivers/video/sis/sis_main.c
index a531a0f..900b3a0 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);
 
-- 
1.7.3.3

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