* [PATCH v2 net 1/2] ieee802154: 6lowpan: look up the neighbour short address in lowpan_xmit()
2026-10-02 8:27 [PATCH v2 net 0/2] ieee802154: 6lowpan: fix transmit address handling Eric Dumazet
@ 2026-10-02 8:27 ` Eric Dumazet
2026-10-02 8:27 ` [PATCH v2 net 2/2] 6lowpan: fix warning in lowpan_compress_addr_64() Eric Dumazet
1 sibling, 0 replies; 3+ messages in thread
From: Eric Dumazet @ 2026-10-02 8:27 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni, Alexander Aring
Cc: Simon Horman, netdev, edumazet, Eric Dumazet
lowpan_header_create() uses ipv6_hdr(skb)->daddr to find the
neighbour, and to use its 802.15.4 short address if it has one.
The IPv6 header is not there yet when lowpan_header_create() is
called for AF_PACKET SOCK_DGRAM sockets: packet_snd() copies the
payload after dev_hard_header(), and tpacket_fill_skb() attaches it
as page fragments after dev_hard_header(). The lookup then reads
uninitialized memory, possibly past the end of the linear data.
Move the lookup to lowpan_header(), called from lowpan_xmit().
lowpan_xmit() now makes sure the IPv6 header is in the linear part
of the skb.
Fixes: eab560e58208 ("6lowpan: add support for 802.15.4 short addr handling")
Signed-off-by: Eric Dumazet <edumazet@kernel.org>
Cc: Alexander Aring <alex.aring@gmail.com>
---
net/ieee802154/6lowpan/tx.c | 62 +++++++++++++++++++++----------------
1 file changed, 36 insertions(+), 26 deletions(-)
diff --git a/net/ieee802154/6lowpan/tx.c b/net/ieee802154/6lowpan/tx.c
index 4df76ff50699ede5c187c9cca6f0cc10b19d2123..ab28b6f912c000f5cf141982b6d1b25e7d2e48f6 100644
--- a/net/ieee802154/6lowpan/tx.c
+++ b/net/ieee802154/6lowpan/tx.c
@@ -36,9 +36,6 @@ int lowpan_header_create(struct sk_buff *skb, struct net_device *ldev,
{
struct wpan_dev *wpan_dev = lowpan_802154_dev(ldev)->wdev->ieee802154_ptr;
struct lowpan_addr_info *info = lowpan_skb_priv(skb);
- struct lowpan_802154_neigh *llneigh = NULL;
- const struct ipv6hdr *hdr = ipv6_hdr(skb);
- struct neighbour *n;
if (!daddr)
return -EINVAL;
@@ -57,28 +54,12 @@ int lowpan_header_create(struct sk_buff *skb, struct net_device *ldev,
info->daddr.short_addr = cpu_to_le16(IEEE802154_ADDR_BROADCAST);
info->daddr.mode = IEEE802154_ADDR_SHORT;
} else {
- __le16 short_addr = cpu_to_le16(IEEE802154_ADDR_SHORT_UNSPEC);
-
- n = neigh_lookup(&nd_tbl, &hdr->daddr, ldev);
- if (n) {
- llneigh = lowpan_802154_neigh(neighbour_priv(n));
- read_lock_bh(&n->lock);
- short_addr = llneigh->short_addr;
- read_unlock_bh(&n->lock);
- }
-
- if (llneigh &&
- lowpan_802154_is_valid_src_short_addr(short_addr)) {
- info->daddr.short_addr = short_addr;
- info->daddr.mode = IEEE802154_ADDR_SHORT;
- } else {
- info->daddr.mode = IEEE802154_ADDR_LONG;
- ieee802154_be64_to_le64(&info->daddr.extended_addr,
- daddr);
- }
-
- if (n)
- neigh_release(n);
+ /* The IPv6 header might not be there yet (AF_PACKET).
+ * lowpan_header() will use the neighbour short address,
+ * if there is one.
+ */
+ info->daddr.mode = IEEE802154_ADDR_LONG;
+ ieee802154_be64_to_le64(&info->daddr.extended_addr, daddr);
}
if (!saddr) {
@@ -221,6 +202,31 @@ lowpan_xmit_fragmented(struct sk_buff *skb, struct net_device *ldev,
return rc;
}
+/* Use the short address of the IPv6 destination, if the neighbour has one. */
+static void lowpan_neigh_short_addr(const struct sk_buff *skb,
+ struct net_device *ldev,
+ struct ieee802154_addr *daddr)
+{
+ struct lowpan_802154_neigh *llneigh;
+ struct neighbour *n;
+ __le16 short_addr;
+
+ n = neigh_lookup(&nd_tbl, &ipv6_hdr(skb)->daddr, ldev);
+ if (!n)
+ return;
+
+ llneigh = lowpan_802154_neigh(neighbour_priv(n));
+ read_lock_bh(&n->lock);
+ short_addr = llneigh->short_addr;
+ read_unlock_bh(&n->lock);
+ neigh_release(n);
+
+ if (lowpan_802154_is_valid_src_short_addr(short_addr)) {
+ daddr->short_addr = short_addr;
+ daddr->mode = IEEE802154_ADDR_SHORT;
+ }
+}
+
static int lowpan_header(struct sk_buff *skb, struct net_device *ldev,
u16 *dgram_size, u16 *dgram_offset)
{
@@ -230,6 +236,9 @@ static int lowpan_header(struct sk_buff *skb, struct net_device *ldev,
memcpy(&info, lowpan_skb_priv(skb), sizeof(info));
+ if (info.daddr.mode == IEEE802154_ADDR_LONG)
+ lowpan_neigh_short_addr(skb, ldev, &info.daddr);
+
*dgram_size = skb->len;
lowpan_header_compress(skb, ldev, &info.daddr, &info.saddr);
/* dgram_offset = (saved bytes after compression) + lowpan header len */
@@ -255,7 +264,8 @@ netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *ldev)
pr_debug("package xmit\n");
- if (skb->protocol != htons(ETH_P_IPV6)) {
+ if (skb->protocol != htons(ETH_P_IPV6) ||
+ !pskb_network_may_pull(skb, sizeof(struct ipv6hdr))) {
kfree_skb(skb);
return NET_XMIT_DROP;
}
--
2.56.0.rc1.315.gc6ed9934b7-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v2 net 2/2] 6lowpan: fix warning in lowpan_compress_addr_64()
2026-10-02 8:27 [PATCH v2 net 0/2] ieee802154: 6lowpan: fix transmit address handling Eric Dumazet
2026-10-02 8:27 ` [PATCH v2 net 1/2] ieee802154: 6lowpan: look up the neighbour short address in lowpan_xmit() Eric Dumazet
@ 2026-10-02 8:27 ` Eric Dumazet
1 sibling, 0 replies; 3+ messages in thread
From: Eric Dumazet @ 2026-10-02 8:27 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni, Alexander Aring
Cc: Simon Horman, netdev, edumazet, Eric Dumazet, Farhad Alemi
SEFCOM lab reported a warning in lowpan_compress_addr_64():
WARNING: net/6lowpan/iphc.c:937 at lowpan_iphc_compress_802154_lladdr net/6lowpan/iphc.c:937 [inline]
WARNING: net/6lowpan/iphc.c:937 at lowpan_compress_addr_64+0x4be/0x9c0 net/6lowpan/iphc.c:952
Call Trace:
lowpan_compress_addr_64+0x4be/0x9c0 net/6lowpan/iphc.c:952
lowpan_header_compress+0xeef/0x1ef0 net/6lowpan/iphc.c:1242
lowpan_header net/ieee802154/6lowpan/tx.c:234 [inline]
lowpan_xmit+0x4c6/0x1420 net/ieee802154/6lowpan/tx.c:282
dev_hard_start_xmit+0x23b/0x620 net/core/dev.c:3904
__dev_queue_xmit+0x11e7/0x3250 net/core/dev.c:4870
packet_snd net/packet/af_packet.c:3082 [inline]
packet_sendmsg+0x3d9b/0x5150 net/packet/af_packet.c:3114
lowpan_header_create() stores the 802.15.4 addresses in the skb
headroom, without changing skb->data, and lowpan_xmit() reads them
from there. But lowpan_xmit() cannot know if this was done:
- AF_PACKET SOCK_RAW sockets do not call dev_hard_header().
- GSO segments get a new headroom: skb_segment() only copies
data starting at the mac header.
lowpan_xmit() then uses uninitialized memory, and can call
lowpan_header_compress() with invalid address modes.
Fix this by pushing the destination address as a pseudo header,
like IPoIB in ipoib_hard_header(). The pseudo header is the 8 byte
EUI-64 given to dev_hard_header(), as in sockaddr_ll.sll_addr,
so its layout does not depend on the architecture.
lowpan_xmit() pulls it, then lowpan_header() computes the 802.15.4
addresses like lowpan_header_create() did. Like IPoIB, the saddr
argument is ignored: the IPv6 stack and AF_PACKET pass NULL, and
the wpan device address is used.
Set hard_header_len to the pseudo header size, so that AF_PACKET
SOCK_RAW sockets set the network header after it, and probe the
transport header from there. lowpan_xmit() now checks the minimum
length itself, and resets the network header after pulling the
pseudo header: lowpan_header_compress() expects the IPv6 header
at skb->data.
Also return -EINVAL from lowpan_header_create() for non IPv6
packets, like net/bluetooth/6lowpan.c, instead of returning 0
without a pseudo header. lowpan_xmit() drops them anyway.
IPv6 stack and AF_PACKET SOCK_DGRAM users are not affected.
AF_PACKET SOCK_RAW senders now have to put the destination address
in front of the IPv6 header, and SOCK_RAW packet taps see it
on transmit. Received packets are unchanged: their framing for
SOCK_RAW taps already depends on the 6LoWPAN dispatch type.
tcpdump is not affected, libpcap uses cooked mode for ARPHRD_6LOWPAN.
Fixes: eab560e58208 ("6lowpan: add support for 802.15.4 short addr handling")
Reported-by: Farhad Alemi <falemi@asu.edu>
Closes: https://lore.kernel.org/netdev/CA+0ovChS18paCd=ZE-7j_M-JtFF-N6+A75deKUqJ0Yy7ux=h2Q@mail.gmail.com/
Signed-off-by: Eric Dumazet <edumazet@kernel.org>
Cc: Alexander Aring <alex.aring@gmail.com>
---
net/ieee802154/6lowpan/6lowpan_i.h | 5 ++
net/ieee802154/6lowpan/core.c | 4 +-
net/ieee802154/6lowpan/tx.c | 82 +++++++++++++-----------------
3 files changed, 42 insertions(+), 49 deletions(-)
diff --git a/net/ieee802154/6lowpan/6lowpan_i.h b/net/ieee802154/6lowpan/6lowpan_i.h
index 44a7e16bf3b5e14c03b99a806145203fc2a4af01..ccc49d10983318b1370a659ff61649bf339fb8c7 100644
--- a/net/ieee802154/6lowpan/6lowpan_i.h
+++ b/net/ieee802154/6lowpan/6lowpan_i.h
@@ -30,6 +30,11 @@ struct lowpan_frag_queue {
struct inet_frag_queue q;
};
+/* lowpan_header_create() pushes the destination address (an EUI-64, as in
+ * sockaddr_ll.sll_addr) in front of the IPv6 header, lowpan_xmit() pulls it.
+ */
+#define LOWPAN_PSEUDO_HDR_LEN EUI64_ADDR_LEN
+
int lowpan_frag_rcv(struct sk_buff *skb, const u8 frag_type);
void lowpan_net_frag_exit(void);
int lowpan_net_frag_init(void);
diff --git a/net/ieee802154/6lowpan/core.c b/net/ieee802154/6lowpan/core.c
index 6a8d6852cb93057305a1a6c5398a3c072bde9f0f..c70b5e414fdf2a68013ded7b0d1d51ba3e3f55de 100644
--- a/net/ieee802154/6lowpan/core.c
+++ b/net/ieee802154/6lowpan/core.c
@@ -109,8 +109,8 @@ static const struct net_device_ops lowpan_netdev_ops = {
static void lowpan_setup(struct net_device *ldev)
{
memset(ldev->broadcast, 0xff, IEEE802154_ADDR_LEN);
- /* We need an ipv6hdr as minimum len when calling xmit */
- ldev->hard_header_len = sizeof(struct ipv6hdr);
+ /* lowpan_header_create() pushes the destination address */
+ ldev->hard_header_len = LOWPAN_PSEUDO_HDR_LEN;
ldev->flags = IFF_BROADCAST | IFF_MULTICAST;
ldev->priv_flags |= IFF_NO_QUEUE;
diff --git a/net/ieee802154/6lowpan/tx.c b/net/ieee802154/6lowpan/tx.c
index ab28b6f912c000f5cf141982b6d1b25e7d2e48f6..10ce2928fcca1a9fd535e8e35f2cac3f792e82f6 100644
--- a/net/ieee802154/6lowpan/tx.c
+++ b/net/ieee802154/6lowpan/tx.c
@@ -15,17 +15,13 @@ struct lowpan_addr_info {
struct ieee802154_addr saddr;
};
-static inline struct
-lowpan_addr_info *lowpan_skb_priv(const struct sk_buff *skb)
-{
- WARN_ON_ONCE(skb_headroom(skb) < sizeof(struct lowpan_addr_info));
- return (struct lowpan_addr_info *)(skb->data -
- sizeof(struct lowpan_addr_info));
-}
-
/* This callback will be called from AF_PACKET and IPv6 stack, the AF_PACKET
* sockets gives an 8 byte array for addresses only!
*
+ * Like IPoIB, the destination address is pushed as a pseudo header, which
+ * AF_PACKET SOCK_RAW senders have to provide. lowpan_xmit() pulls it, and
+ * always uses the wpan device address as source address.
+ *
* TODO I think AF_PACKET DGRAM (sending/receiving) RAW (sending) makes no
* sense here. We should disable it, the right use-case would be AF_INET6
* RAW/DGRAM sockets.
@@ -34,9 +30,6 @@ int lowpan_header_create(struct sk_buff *skb, struct net_device *ldev,
unsigned short type, const void *daddr,
const void *saddr, unsigned int len)
{
- struct wpan_dev *wpan_dev = lowpan_802154_dev(ldev)->wdev->ieee802154_ptr;
- struct lowpan_addr_info *info = lowpan_skb_priv(skb);
-
if (!daddr)
return -EINVAL;
@@ -44,38 +37,11 @@ int lowpan_header_create(struct sk_buff *skb, struct net_device *ldev,
* if this package isn't ipv6 one, where should it be routed?
*/
if (type != ETH_P_IPV6)
- return 0;
-
- /* intra-pan communication */
- info->saddr.pan_id = wpan_dev->pan_id;
- info->daddr.pan_id = info->saddr.pan_id;
-
- if (!memcmp(daddr, ldev->broadcast, EUI64_ADDR_LEN)) {
- info->daddr.short_addr = cpu_to_le16(IEEE802154_ADDR_BROADCAST);
- info->daddr.mode = IEEE802154_ADDR_SHORT;
- } else {
- /* The IPv6 header might not be there yet (AF_PACKET).
- * lowpan_header() will use the neighbour short address,
- * if there is one.
- */
- info->daddr.mode = IEEE802154_ADDR_LONG;
- ieee802154_be64_to_le64(&info->daddr.extended_addr, daddr);
- }
-
- if (!saddr) {
- if (lowpan_802154_is_valid_src_short_addr(wpan_dev->short_addr)) {
- info->saddr.mode = IEEE802154_ADDR_SHORT;
- info->saddr.short_addr = wpan_dev->short_addr;
- } else {
- info->saddr.mode = IEEE802154_ADDR_LONG;
- info->saddr.extended_addr = wpan_dev->extended_addr;
- }
- } else {
- info->saddr.mode = IEEE802154_ADDR_LONG;
- ieee802154_be64_to_le64(&info->saddr.extended_addr, saddr);
- }
+ return -EINVAL;
- return 0;
+ memcpy(skb_push(skb, LOWPAN_PSEUDO_HDR_LEN), daddr,
+ LOWPAN_PSEUDO_HDR_LEN);
+ return LOWPAN_PSEUDO_HDR_LEN;
}
static struct sk_buff*
@@ -228,16 +194,32 @@ static void lowpan_neigh_short_addr(const struct sk_buff *skb,
}
static int lowpan_header(struct sk_buff *skb, struct net_device *ldev,
- u16 *dgram_size, u16 *dgram_offset)
+ const u8 *daddr, u16 *dgram_size, u16 *dgram_offset)
{
struct wpan_dev *wpan_dev = lowpan_802154_dev(ldev)->wdev->ieee802154_ptr;
struct ieee802154_mac_cb *cb = mac_cb_init(skb);
struct lowpan_addr_info info;
- memcpy(&info, lowpan_skb_priv(skb), sizeof(info));
+ /* intra-pan communication */
+ info.saddr.pan_id = wpan_dev->pan_id;
+ info.daddr.pan_id = info.saddr.pan_id;
- if (info.daddr.mode == IEEE802154_ADDR_LONG)
+ if (!memcmp(daddr, ldev->broadcast, EUI64_ADDR_LEN)) {
+ info.daddr.short_addr = cpu_to_le16(IEEE802154_ADDR_BROADCAST);
+ info.daddr.mode = IEEE802154_ADDR_SHORT;
+ } else {
+ info.daddr.mode = IEEE802154_ADDR_LONG;
+ ieee802154_be64_to_le64(&info.daddr.extended_addr, daddr);
lowpan_neigh_short_addr(skb, ldev, &info.daddr);
+ }
+
+ if (lowpan_802154_is_valid_src_short_addr(wpan_dev->short_addr)) {
+ info.saddr.mode = IEEE802154_ADDR_SHORT;
+ info.saddr.short_addr = wpan_dev->short_addr;
+ } else {
+ info.saddr.mode = IEEE802154_ADDR_LONG;
+ info.saddr.extended_addr = wpan_dev->extended_addr;
+ }
*dgram_size = skb->len;
lowpan_header_compress(skb, ldev, &info.daddr, &info.saddr);
@@ -258,6 +240,7 @@ static int lowpan_header(struct sk_buff *skb, struct net_device *ldev,
netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *ldev)
{
+ u8 daddr[LOWPAN_PSEUDO_HDR_LEN];
struct ieee802154_hdr wpan_hdr;
int max_single, ret;
u16 dgram_size, dgram_offset;
@@ -265,11 +248,16 @@ netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *ldev)
pr_debug("package xmit\n");
if (skb->protocol != htons(ETH_P_IPV6) ||
- !pskb_network_may_pull(skb, sizeof(struct ipv6hdr))) {
+ !pskb_may_pull(skb, sizeof(daddr) + sizeof(struct ipv6hdr))) {
kfree_skb(skb);
return NET_XMIT_DROP;
}
+ /* Destination address pushed by lowpan_header_create() */
+ memcpy(daddr, skb->data, sizeof(daddr));
+ __skb_pull(skb, sizeof(daddr));
+ skb_reset_network_header(skb);
+
WARN_ON_ONCE(skb->len > IPV6_MIN_MTU);
/* We must take a copy of the skb before we modify/replace the ipv6
@@ -294,7 +282,7 @@ netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *ldev)
return NET_XMIT_DROP;
}
- ret = lowpan_header(skb, ldev, &dgram_size, &dgram_offset);
+ ret = lowpan_header(skb, ldev, daddr, &dgram_size, &dgram_offset);
if (ret < 0) {
kfree_skb(skb);
return NET_XMIT_DROP;
--
2.56.0.rc1.315.gc6ed9934b7-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread