b43: stop format string leaking into error msgs

The module parameter "fwpostfix" is userspace controllable, unfiltered,
and is used to define the firmware filename. b43_do_request_fw() populates
ctx->errors[] on error, containing the firmware filename. b43err()
parses its arguments as a format string. For systems with b43 hardware,
this could lead to a uid-0 to ring-0 escalation.

CVE-2013-2852

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/b43/main.c b/drivers/net/wireless/b43/main.c
index 6dd07e2..a95b77a 100644 (file)
--- a/drivers/net/wireless/b43/main.c
+++ b/drivers/net/wireless/b43/main.c
@@ -2458,7 +2458,7 @@ static void b43_request_firmware(struct work_struct *work)
        for (i = 0; i < B43_NR_FWTYPES; i++) {
                errmsg = ctx->errors[i];
                if (strlen(errmsg))
-                       b43err(dev->wl, errmsg);
+                       b43err(dev->wl, "%s", errmsg);
        }
        b43_print_fw_helptext(dev->wl, 1);
        goto out;