From 0d189b4451f424bdb4296a0c791b9cd731bc317e Mon Sep 17 00:00:00 2001 From: Oliver Hartkopp Date: Mon, 5 Jan 2015 18:40:15 +0100 Subject: [PATCH 1/1] can: dev: fix crtlmode_supported check commit 9b1087aa5e86448fe6ad40a58964e35f3ba423d5 upstream. When changing flags in the CAN drivers ctrlmode the provided new content has to be checked whether the bits are allowed to be changed. The bits that are to be changed are given as a bitfield in cm->mask. Therefore checking against cm->flags is wrong as the content can hold any kind of values. The iproute2 tool sets the bits in cm->mask and cm->flags depending on the detected command line options. To be robust against bogus user space applications additionally sanitize the provided flags with the provided mask. Cc: Wolfgang Grandegger Signed-off-by: Oliver Hartkopp Signed-off-by: Marc Kleine-Budde [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- drivers/net/can/dev.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index 1eac27ff7724..a25442ed4e7e 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c @@ -605,10 +605,14 @@ static int can_changelink(struct net_device *dev, if (dev->flags & IFF_UP) return -EBUSY; cm = nla_data(data[IFLA_CAN_CTRLMODE]); - if (cm->flags & ~priv->ctrlmode_supported) + + /* check whether changed bits are allowed to be modified */ + if (cm->mask & ~priv->ctrlmode_supported) return -EOPNOTSUPP; + + /* clear bits to be modified and copy the flag values */ priv->ctrlmode &= ~cm->mask; - priv->ctrlmode |= cm->flags; + priv->ctrlmode |= (cm->flags & cm->mask); } if (data[IFLA_CAN_BITTIMING]) { -- 2.39.2