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Date: Mon, 16 Jan 2017 16:25:55 -0500
From: "J. Bruce Fields" <bfields@...ldses.org>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Thomas Sailer <t.sailer@...mni.ethz.ch>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Johan Hovold <johan@...nel.org>, Alex Elder <elder@...nel.org>,
Jeff Layton <jlayton@...chiereds.net>,
David Howells <dhowells@...hat.com>, NeilBrown <neilb@...e.com>
Subject: Re: [PATCH 2/3] Make static usermode helper binaries constant
On Mon, Jan 16, 2017 at 05:50:31PM +0100, Greg KH wrote:
> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> There are a number of usermode helper binaries that are "hard coded" in
> the kernel today, so mark them as "const" to make it harder for someone
> to change where the variables point to.
>
...
> --- a/drivers/pnp/pnpbios/core.c
> +++ b/drivers/pnp/pnpbios/core.c
> @@ -98,6 +98,7 @@ static struct completion unload_sem;
> */
> static int pnp_dock_event(int dock, struct pnp_docking_station_info *info)
> {
> + static char const sbin_pnpbios[] = "/sbin/pnpbios";
> char *argv[3], **envp, *buf, *scratch;
> int i = 0, value;
>
> @@ -112,7 +113,7 @@ static int pnp_dock_event(int dock, struct pnp_docking_station_info *info)
> * integrated into the driver core and use the usual infrastructure
> * like sysfs and uevents
> */
> - argv[0] = "/sbin/pnpbios";
> + argv[0] = (char *)sbin_pnpbios;
So here and elsewhere, can attackers write to argv[0] instead of to the
memory where the string lives?
Apologies if I'm rehashing earlier discussion, I did a quick search of
archives but could easily have missed something.
--b.
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