linux-kernel - [PATCH v2] drivers/video/via/ioctl.c: prevent reading uninitialized stack memory

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Message-ID: <1284592104.10727.12.camel@dan>
Date:	Wed, 15 Sep 2010 19:08:24 -0400
From:	Dan Rosenberg <drosenberg@...curity.com>
To:	JosephChan@....com.tw, ScottFang@...tech.com.cn,
	FlorianSchandinat@....de
Cc:	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	security@...nel.org, stable@...nel.org
Subject: [PATCH v2] drivers/video/via/ioctl.c: prevent reading
 uninitialized stack memory

Disregard previous version, which had a typo and wouldn't compile.
Also, math is fun: the ioctl allows reading of 1968 BITS = 246 bytes,
not 1968 bytes as previously reported.

The VIAFB_GET_INFO device ioctl allows unprivileged users to read 246
bytes of uninitialized stack memory, because the "reserved" member of
the viafb_ioctl_info 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/via/ioctl.c	2010-08-26 19:47:12.000000000 -0400
+++ linux-2.6.35.4/drivers/video/via/ioctl.c	2010-09-15 11:53:29.997375748 -0400
@@ -25,6 +25,8 @@ int viafb_ioctl_get_viafb_info(u_long ar
 {
 	struct viafb_ioctl_info viainfo;
 
+	memset(&viainfo, 0, sizeof(struct viafb_ioctl_info));
+
 	viainfo.viafb_id = VIAID;
 	viainfo.vendor_id = PCI_VIA_VENDOR_ID;
 


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