linux-kernel - [110/127] V4L/DVB: ivtvfb: prevent reading uninitialized stack memory

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Date:	Tue, 07 Dec 2010 16:44:56 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Dan Rosenberg <dan.j.rosenberg@...il.com>,
	Andy Walls <awalls@...metrocast.net>,
	Mauro Carvalho Chehab <mchehab@...hat.com>
Subject: [110/127] V4L/DVB: ivtvfb: prevent reading uninitialized stack memory

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

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

commit 405707985594169cfd0b1d97d29fcb4b4c6f2ac9 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>
Signed-off-by: Andy Walls <awalls@...metrocast.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/media/video/ivtv/ivtvfb.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/media/video/ivtv/ivtvfb.c
+++ b/drivers/media/video/ivtv/ivtvfb.c
@@ -457,6 +457,8 @@ static int ivtvfb_ioctl(struct fb_info *
 			struct fb_vblank vblank;
 			u32 trace;
 
+			memset(&vblank, 0, sizeof(struct fb_vblank));
+
 			vblank.flags = FB_VBLANK_HAVE_COUNT |FB_VBLANK_HAVE_VCOUNT |
 					FB_VBLANK_HAVE_VSYNC;
 			trace = read_reg(0x028c0) >> 16;


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