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authorOliver Hartkopp <socketcan@hartkopp.net>2019-12-07 21:34:18 +0300
committerMarc Kleine-Budde <mkl@pengutronix.de>2020-01-02 17:34:27 +0300
commite7153bf70c3496bac00e7e4f395bb8d8394ac0ea (patch)
tree916e307b02f8f88d6db4ce4878104be0f4cd31f4 /include/linux/can
parent93bdc0eb0b4bb5e7094fd4a95f4a394e4a927e09 (diff)
downloadlinux-e7153bf70c3496bac00e7e4f395bb8d8394ac0ea.tar.xz
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: d3b58c47d330d ("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>
Diffstat (limited to 'include/linux/can')
-rw-r--r--include/linux/can/dev.h34
1 files changed, 34 insertions, 0 deletions
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 9b3c720a31b1..5e3d45525bd3 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -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: