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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , b.a.t.m.a.n@lists.open-mesh.org, Sven Eckelmann , Simon Wunderlich Subject: [PATCH net-next 11/15] batman-adv: annotate functions which may reallocate the skbuff Date: Tue, 28 Jul 2026 15:39:14 +0200 Message-ID: <20260728133918.643267-12-sw@simonwunderlich.de> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260728133918.643267-1-sw@simonwunderlich.de> References: <20260728133918.643267-1-sw@simonwunderlich.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: AT4O2L75LXNXCT57QPJH27UDJNHMAJ2D X-Message-ID-Hash: AT4O2L75LXNXCT57QPJH27UDJNHMAJ2D X-MailFrom: sw@simonwunderlich.de X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; header-match-b.a.t.m.a.n.lists.open-mesh.org-0; header-match-b.a.t.m.a.n.lists.open-mesh.org-1; header-match-b.a.t.m.a.n.lists.open-mesh.org-2; header-match-b.a.t.m.a.n.lists.open-mesh.org-3; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: The list for a Better Approach To Mobile Ad-hoc Networking Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: Sven Eckelmann When a function is called which reallocated the skbuff, it is necessary to reacquire the pointers into the skb data. Otherwise they might cause an use-after-free. But is hard to identify such case when it is not clear that helpers are actually using skb-reallocating functions. Signed-off-by: Sven Eckelmann Signed-off-by: Simon Wunderlich --- net/batman-adv/bridge_loop_avoidance.c | 10 +++++++ net/batman-adv/distributed-arp-table.c | 40 ++++++++++++++++++++++++++ net/batman-adv/gateway_client.c | 6 +++- net/batman-adv/main.c | 5 ++++ net/batman-adv/mesh-interface.c | 5 ++++ net/batman-adv/multicast_forw.c | 10 +++++++ net/batman-adv/routing.c | 10 +++++++ 7 files changed, 85 insertions(+), 1 deletion(-) diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c index 8ee3ec5eb2c5e..18eafbeeccfdd 100644 --- a/net/batman-adv/bridge_loop_avoidance.c +++ b/net/batman-adv/bridge_loop_avoidance.c @@ -1087,6 +1087,11 @@ static int batadv_check_claim_group(struct batadv_priv *bat_priv, * @primary_if: the primary hard interface of this batman mesh interface * @skb: the frame to be checked * + * Warning: This function may reallocate the skb data buffer via + * batadv_get_vid(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: true if it was a claim frame, otherwise return false to * tell the callee that it can use the frame on its own. */ @@ -1816,6 +1821,11 @@ bool batadv_bla_is_backbone_gw_orig(struct batadv_priv *bat_priv, u8 *orig, * @orig_node: the orig_node of the frame * @hdr_size: maximum length of the frame * + * Warning: This function may reallocate the skb data buffer via + * pskb_may_pull() and batadv_get_vid(). Any pointer into the skb data (e.g. + * obtained from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: true if the orig_node is also a gateway on the mesh interface, * otherwise it returns false. */ diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c index 0251cdf5542bb..e9cc4690068eb 100644 --- a/net/batman-adv/distributed-arp-table.c +++ b/net/batman-adv/distributed-arp-table.c @@ -1039,6 +1039,11 @@ int batadv_dat_cache_dump(struct sk_buff *msg, struct netlink_callback *cb) * @skb: packet to analyse * @hdr_size: size of the possible header before the ARP packet in the skb * + * Warning: This function may reallocate the skb data buffer via + * pskb_may_pull(). Any pointer into the skb data (e.g. obtained from skb->data + * or eth_hdr()) before this call must be considered invalid afterwards and has + * to be reacquired. + * * Return: the ARP type if the skb contains a valid ARP packet, 0 otherwise. */ static u16 batadv_arp_get_type(struct batadv_priv *bat_priv, @@ -1115,6 +1120,11 @@ static u16 batadv_arp_get_type(struct batadv_priv *bat_priv, * The caller must ensure that at least @hdr_size + ETH_HLEN bytes are * accessible after skb->data. * + * Warning: This function calls batadv_get_vid() and may therefore reallocate + * the skb data buffer. Any pointer into the skb data (e.g. obtained from + * skb->data or eth_hdr()) before this call must be considered invalid + * afterwards and has to be reacquired. + * * Return: If the packet embedded in the skb is vlan tagged this function * returns the VID with the BATADV_VLAN_HAS_TAG flag. Otherwise BATADV_NO_FLAGS * is returned. @@ -1177,6 +1187,11 @@ batadv_dat_arp_create_reply(struct batadv_priv *bat_priv, __be32 ip_src, * @bat_priv: the bat priv with all the mesh interface information * @skb: packet to check * + * Warning: This function may reallocate the skb data buffer via + * batadv_dat_get_vid(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: true if the message has been sent to the dht candidates, false * otherwise. In case of a positive return value the message has to be enqueued * to permit the fallback. @@ -1282,6 +1297,11 @@ bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv, * @skb: packet to check * @hdr_size: size of the encapsulation header * + * Warning: This function may reallocate the skb data buffer via + * batadv_dat_get_vid(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: true if the request has been answered, false otherwise. */ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv, @@ -1349,6 +1369,11 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv, * batadv_dat_snoop_outgoing_arp_reply() - snoop the ARP reply and fill the DHT * @bat_priv: the bat priv with all the mesh interface information * @skb: packet to check + * + * Warning: This function may reallocate the skb data buffer via + * batadv_dat_get_vid(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. */ void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv, struct sk_buff *skb) @@ -1398,6 +1423,11 @@ void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv, * @skb: packet to check * @hdr_size: size of the encapsulation header * + * Warning: This function may reallocate the skb data buffer via + * batadv_dat_get_vid(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: true if the packet was snooped and consumed by DAT. False if the * packet has to be delivered to the interface */ @@ -1812,6 +1842,11 @@ void batadv_dat_snoop_outgoing_dhcp_ack(struct batadv_priv *bat_priv, * This function first checks whether the given skb is a valid DHCPACK. If * so then its source MAC and IP as well as its DHCP Client Hardware Address * field and DHCP Your IP Address field are added to the local DAT cache. + * + * Warning: This function may reallocate the skb data buffer via + * pskb_may_pull()/batadv_dat_get_vid(). Any pointer into the skb data (e.g. + * obtained from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. */ void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv, struct sk_buff *skb, int hdr_size) @@ -1859,6 +1894,11 @@ void batadv_dat_snoop_incoming_dhcp_ack(struct batadv_priv *bat_priv, * @bat_priv: the bat priv with all the mesh interface information * @forw_packet: the broadcast packet * + * Warning: This function may reallocate the skb data buffer via + * batadv_dat_get_vid(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: true if the node can drop the packet, false otherwise. */ bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv, diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c index 48fc711b8fd62..f4d53d9ea3b31 100644 --- a/net/batman-adv/gateway_client.c +++ b/net/batman-adv/gateway_client.c @@ -677,7 +677,11 @@ batadv_gw_dhcp_recipient_get(struct sk_buff *skb, unsigned int *header_len, * server. Due to topology changes it may be the case that the GW server * previously selected is not the best one anymore. * - * This call might reallocate skb data. + * Warning: This function may reallocate the skb data buffer via + * batadv_get_vid(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Must be invoked only when the DHCP packet is going TO a DHCP SERVER. * * Return: true if the packet destination is unicast and it is not the best gw, diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c index c5f4e9f8728c0..fa82ffb706b3f 100644 --- a/net/batman-adv/main.c +++ b/net/batman-adv/main.c @@ -610,6 +610,11 @@ void batadv_recv_handler_unregister(u8 packet_type) * The caller must ensure that at least @header_len + ETH_HLEN bytes are * accessible after skb->data. * + * Warning: This function may reallocate the skb data buffer via + * pskb_may_pull(). Any pointer into the skb data (e.g. obtained from skb->data + * or eth_hdr()) before this call must be considered invalid afterwards and has + * to be reacquired. + * * Return: VID with the BATADV_VLAN_HAS_TAG flag when the packet embedded in the * skb is vlan tagged. Otherwise BATADV_NO_FLAGS. */ diff --git a/net/batman-adv/mesh-interface.c b/net/batman-adv/mesh-interface.c index 667ea5704fbdb..982de90906b59 100644 --- a/net/batman-adv/mesh-interface.c +++ b/net/batman-adv/mesh-interface.c @@ -57,6 +57,11 @@ * @skb: packet buffer which should be modified * @len: number of bytes to add * + * Warning: This function may reallocate the skb data buffer via + * skb_cow_head(). Any pointer into the skb data (e.g. obtained + * from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: 0 on success or negative error number in case of failure */ int batadv_skb_head_push(struct sk_buff *skb, unsigned int len) diff --git a/net/batman-adv/multicast_forw.c b/net/batman-adv/multicast_forw.c index c99579dc1ca98..75a3a4567b08b 100644 --- a/net/batman-adv/multicast_forw.c +++ b/net/batman-adv/multicast_forw.c @@ -1080,6 +1080,11 @@ unsigned int batadv_mcast_forw_packet_hdrlen(unsigned int num_dests) * Tries to expand an skb's headroom so that its head to tail is 1298 * bytes (minimum IPv6 MTU + vlan ethernet header size) large. * + * Warning: This function may reallocate the skb data buffer via + * skb_cow() / skb_linearize(). Any pointer into the skb data (e.g. + * obtained from skb->data or eth_hdr()) before this call must be + * considered invalid afterwards and has to be reacquired. + * * Return: -EINVAL if the given skb's length is too large or -ENOMEM on memory * allocation failure. Otherwise, on success, zero is returned. */ @@ -1123,6 +1128,11 @@ static int batadv_mcast_forw_expand_head(struct batadv_priv *bat_priv, * that signaled interest in it, that is either via the translation table or the * according want-all flags, is attached accordingly. * + * Warning: This function may reallocate the skb data buffer via + * batadv_mcast_forw_expand_head(). Any pointer into the skb data (e.g. + * obtained from skb->data or eth_hdr()) before this call must be + * considered invalid afterwards and has to be reacquired. + * * Return: true on success, false otherwise. */ bool batadv_mcast_forw_push(struct batadv_priv *bat_priv, struct sk_buff *skb, diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c index c1114ee575478..770037b8ca4e4 100644 --- a/net/batman-adv/routing.c +++ b/net/batman-adv/routing.c @@ -172,6 +172,11 @@ bool batadv_window_protected(struct batadv_priv *bat_priv, s32 seq_num_diff, * @hard_iface: incoming hard interface * @header_len: minimal header length of packet type * + * Warning: This function may reallocate the skb data buffer via + * skb_cow() / skb_linearize(). Any pointer into the skb data (e.g. + * obtained from skb->data or eth_hdr()) before this call must be + * considered invalid afterwards and has to be reacquired. + * * Return: true when management preconditions are met, false otherwise */ bool batadv_check_management_packet(struct sk_buff *skb, @@ -863,6 +868,11 @@ batadv_reroute_unicast_packet(struct batadv_priv *bat_priv, struct sk_buff *skb, * @skb: the unicast packet to check * @hdr_len: length of the unicast header preceding the payload * + * Warning: This function may reallocate the skb data buffer via + * pskb_may_pull() and batadv_get_vid(). Any pointer into the skb data (e.g. + * obtained from skb->data or eth_hdr()) before this call must be considered + * invalid afterwards and has to be reacquired. + * * Return: true if the packet may be processed further, false if it has been * consumed or has to be dropped by the caller */ -- 2.47.3