From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Tobias Schandinat Date: Wed, 15 Sep 2010 22:42:12 +0000 Subject: Re: [PATCH] drivers/video/via/ioctl.c: prevent reading uninitialized Message-Id: <4C914BC4.8070809@gmx.de> List-Id: References: <1284587059.6275.101.camel@dan> In-Reply-To: <1284587059.6275.101.camel@dan> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dan Rosenberg Cc: JosephChan@via.com.tw, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, security@kernel.org, stable@kernel.org Hi, Dan Rosenberg schrieb: > The VIAFB_GET_INFO device ioctl allows unprivileged users to read 1968 > 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. I am wondering about the number of bytes as sizeof(struct viafb_ioctl_info) = 256 so it should be a bit less. But that's just nitpicking, the issue is certainly real. Your patch does the right thing but there is a bug in it: > Signed-off-by: Dan Rosenberg > > --- 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)); Shouldn't it be sizeof(struct viafb_ioctl_info) or sizeof(viainfo) ? At least here it does not even compile otherwise.... Thanks, Florian Tobias Schandinat