From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vasiliy Kulikov Date: Sun, 17 Oct 2010 15:38:39 +0000 Subject: Re: [PATCH 6/8] char: synclink: fix information leak to userland Message-Id: <20101017153839.GA11029@albatros> List-Id: References: <1287326493-8134-1-git-send-email-segooon@gmail.com> <4CBB177C.9050007@suse.cz> In-Reply-To: <4CBB177C.9050007@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jiri Slaby Cc: kernel-janitors@vger.kernel.org, Greg Kroah-Hartman , Alan Cox , Arnd Bergmann , linux-kernel@vger.kernel.org On Sun, Oct 17, 2010 at 17:34 +0200, Jiri Slaby wrote: > On 10/17/2010 04:41 PM, Vasiliy Kulikov wrote: > > Structure new_line is copied to userland with some padding fields unitialized. > > It leads to leaking of stack memory. > > I think your tool has a bug. I must admit I fail to see the padding > which would cause leaks. Could you elaborate? I didn't use any tool except "grep copy_to_user" :) typedef struct { unsigned int clock_rate; /* bits per second */ unsigned int clock_type; /* internal, external, TX-internal etc. */ unsigned short loopback; } sync_serial_settings; /* V.35, V.24, X.21 */ On x86_64 sizeof(sync_serial_settings) = 4 + 4 + 2 + 2 = 12. The last 2 is padding. > > > Signed-off-by: Vasiliy Kulikov > > --- > > Compile tested. > > > > drivers/char/synclink.c | 2 ++ > > 1 files changed, 2 insertions(+), 0 deletions(-) > > > > diff --git a/drivers/char/synclink.c b/drivers/char/synclink.c > > index 3a6824f..abd0867 100644 > > --- a/drivers/char/synclink.c > > +++ b/drivers/char/synclink.c > > @@ -7846,6 +7846,8 @@ static int hdlcdev_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd) > > if (cmd != SIOCWANDEV) > > return hdlc_ioctl(dev, ifr, cmd); > > > > + memset(&new_line, 0, size); > > + > > switch(ifr->ifr_settings.type) { > > case IF_GET_IFACE: /* return current sync_serial_settings */ > > > > > -- > js > suse labs -- Vasiliy