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can: can_dropped_invalid_skb(): ensure an initialized headroom in outgoing CAN sk_buffs 

KMSAN sysbot detected a read access to an untinitialized value in the
headroom of an outgoing CAN related sk_buff. When using CAN sockets this
area is filled appropriately - but when using a packet socket this
initialization is missing.

The problematic read access occurs in the CAN receive path which can
only be triggered when the sk_buff is sent through a (virtual) CAN
interface. So we check in the sending path whether we need to perform
the missing initializations.

Fixes: d3b58c47d3 ("can: replace timestamp as unique skb attribute")
Reported-by: syzbot+b02ff0707a97e4e79ebb@syzkaller.appspotmail.com
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: linux-stable <stable@vger.kernel.org> # >= v4.1
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Oliver Hartkopp 2019-12-07 19:34:18 +01:00 committed by Marc Kleine-Budde
parent 93bdc0eb0b
commit e7153bf70c
1 changed files with 34 additions and 0 deletions
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34
include/linux/can/dev.h
View File

@ -18,6 +18,7 @@
#include <linux/can/error.h>
#include <linux/can/led.h>
#include <linux/can/netlink.h>
#include <linux/can/skb.h>
#include <linux/netdevice.h>
/*
@ -91,6 +92,36 @@ struct can_priv {
#define get_can_dlc(i) (min_t(__u8, (i), CAN_MAX_DLC))
#define get_canfd_dlc(i) (min_t(__u8, (i), CANFD_MAX_DLC))
/* Check for outgoing skbs that have not been created by the CAN subsystem */
static inline bool can_skb_headroom_valid(struct net_device *dev,
struct sk_buff *skb)
{
/* af_packet creates a headroom of HH_DATA_MOD bytes which is fine */
if (WARN_ON_ONCE(skb_headroom(skb) < sizeof(struct can_skb_priv)))
return false;
/* af_packet does not apply CAN skb specific settings */
if (skb->ip_summed == CHECKSUM_NONE) {
/* init headroom */
can_skb_prv(skb)->ifindex = dev->ifindex;
can_skb_prv(skb)->skbcnt = 0;
skb->ip_summed = CHECKSUM_UNNECESSARY;
/* preform proper loopback on capable devices */
if (dev->flags & IFF_ECHO)
skb->pkt_type = PACKET_LOOPBACK;
else
skb->pkt_type = PACKET_HOST;
skb_reset_mac_header(skb);
skb_reset_network_header(skb);
skb_reset_transport_header(skb);
}
return true;
}
/* Drop a given socketbuffer if it does not contain a valid CAN frame. */
static inline bool can_dropped_invalid_skb(struct net_device *dev,
struct sk_buff *skb)
@ -108,6 +139,9 @@ static inline bool can_dropped_invalid_skb(struct net_device *dev,
} else
goto inval_skb;
if (!can_skb_headroom_valid(dev, skb))
goto inval_skb;
return false;
inval_skb: