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can_dev: fix crtlmode_supported check

PATCH In review Oliver Hartkopp 2 participants 3 messages Jan 5, 2015 – Jan 7, 2015 CAN network drivers

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Oliver Hartkopp

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#0 lore raw

PATCH 1/1 can_dev: fix crtlmode_supported check

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.

Signed-off-by Oliver Hartkopp <[email protected]>
CC Wolfgang Grandegger <[email protected]>

---

drivers/net/can/dev.c +6 -2
index 3ec8f6f..847c1f8 100644
@@ -807,10 +807,14 @@ 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);
 
 		/* CAN_CTRLMODE_FD can only be set when driver supports FD */
 		if (priv->ctrlmode & CAN_CTRLMODE_FD)
maintainer
#1 lore raw
Quoted 6 lines · Oliver Hartkopp

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.

Quoted 7 lines

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.

Signed-off-by Oliver Hartkopp <[email protected]>
CC Wolfgang Grandegger <[email protected]>

Does not apply to net/master. However I've applied it by hand. v2 will follow.

Marc

Signature · 4 lines
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |
maintainer
#2 lore raw
Quoted 12 lines · Marc Kleine-Budde
Quoted 11 lines · Oliver Hartkopp

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.

Quoted 7 lines
Quoted 2 lines
Signed-off-by Oliver Hartkopp <[email protected]>
CC Wolfgang Grandegger <[email protected]>

Does not apply to net/master. However I've applied it by hand. v2 will follow.

User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.3.0

You should consider to use git send-email instead of thunderbird to post your patches :)

Marc

Signature · 4 lines
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |