The fields of an aggregated OGM(v2) are accessed assuming (at least) 2-byte
alignment, so a following OGM must start at an even offset. As the header
length is even, an odd tvlv_len would misalign it and trigger unaligned
accesses on strict-alignment architectures.
Such a misaligned TVLV/OGM/OGMv2/MCAST is not created by a normal
participant in the mesh. Therefore, reject such malformed packets.
Fixes: 0b6aa0d43767 ("batman-adv: tvlv - basic infrastructure")
Signed-off-by: Sven Eckelmann <[email protected]>
---
Changes in v2:
- also handle batadv_recv_mcast_packet()
- remove RFC
- Link to v1:
https://patch.msgid.link/[email protected]
---
net/batman-adv/bat_iv_ogm.c | 11 ++++++++++-
net/batman-adv/bat_v_ogm.c | 11 ++++++++++-
net/batman-adv/routing.c | 6 ++++++
net/batman-adv/tvlv.c | 6 ++++++
4 files changed, 32 insertions(+), 2 deletions(-)
diff --git a/net/batman-adv/bat_iv_ogm.c b/net/batman-adv/bat_iv_ogm.c
index 7588e64e..bb2f012b 100644
--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -316,14 +316,23 @@ batadv_iv_ogm_aggr_packet(int buff_pos, int packet_len,
const struct batadv_ogm_packet *ogm_packet)
{
int next_buff_pos = 0;
+ u16 tvlv_len;
/* check if there is enough space for the header */
next_buff_pos += buff_pos + sizeof(*ogm_packet);
if (next_buff_pos > packet_len)
return false;
+ tvlv_len = ntohs(ogm_packet->tvlv_len);
+
+ /* the fields of an aggregated OGM are accessed assuming (at least)
+ * 2-byte alignment, so a following OGM must start at an even offset.
+ */
+ if (tvlv_len & 1)
+ return false;
+
/* check if there is enough space for the optional TVLV */
- next_buff_pos += ntohs(ogm_packet->tvlv_len);
+ next_buff_pos += tvlv_len;
return next_buff_pos <= packet_len;
}
diff --git a/net/batman-adv/bat_v_ogm.c b/net/batman-adv/bat_v_ogm.c
index 95efd8a4..037921aa 100644
--- a/net/batman-adv/bat_v_ogm.c
+++ b/net/batman-adv/bat_v_ogm.c
@@ -849,14 +849,23 @@ batadv_v_ogm_aggr_packet(int buff_pos, int packet_len,
const struct batadv_ogm2_packet *ogm2_packet)
{
int next_buff_pos = 0;
+ u16 tvlv_len;
/* check if there is enough space for the header */
next_buff_pos += buff_pos + sizeof(*ogm2_packet);
if (next_buff_pos > packet_len)
return false;
+ tvlv_len = ntohs(ogm2_packet->tvlv_len);
+
+ /* the fields of an aggregated OGMv2 are accessed assuming (at least)
+ * 2-byte alignment, so a following OGMv2 must start at an even offset.
+ */
+ if (tvlv_len & 1)
+ return false;
+
/* check if there is enough space for the optional TVLV */
- next_buff_pos += ntohs(ogm2_packet->tvlv_len);
+ next_buff_pos += tvlv_len;
return next_buff_pos <= packet_len;
}
diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 9db57fd3..c05fcc92 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -1366,6 +1366,12 @@ int batadv_recv_mcast_packet(struct sk_buff *skb,
if (tvlv_buff_len > skb->len - hdr_size)
goto free_skb;
+ /* the fields of an multicast payload are accessed assuming (at least)
+ * 2-byte alignment, so a following packet must start at an even offset.
+ */
+ if (tvlv_buff_len & 1)
+ goto free_skb;
+
ret = batadv_tvlv_containers_process(bat_priv, BATADV_MCAST, NULL, skb,
tvlv_buff, tvlv_buff_len);
if (ret >= 0) {
diff --git a/net/batman-adv/tvlv.c b/net/batman-adv/tvlv.c
index 403c8545..a957555d 100644
--- a/net/batman-adv/tvlv.c
+++ b/net/batman-adv/tvlv.c
@@ -477,6 +477,12 @@ int batadv_tvlv_containers_process(struct batadv_priv
*bat_priv,
if (tvlv_value_cont_len > tvlv_value_len)
break;
+ /* the next tvlv header is accessed assuming (at least) 2-byte
+ * alignment, so it must start at an even offset.
+ */
+ if (tvlv_value_cont_len & 1)
+ break;
+
tvlv_handler = batadv_tvlv_handler_get(bat_priv,
tvlv_hdr->type,
tvlv_hdr->version);
---
base-commit: c7518adb8b6ebdc481f6ed1fc42c7f45099806af
change-id: 20260614-tvlv-2b-align-f11bc4263342
Best regards,
--
Sven Eckelmann <[email protected]>
