[LLC]: skb allocation size for responses

Allocate the skb for llc responses with the received packet size by
using the size adjustable llc_frame_alloc.
Don't allocate useless extra payload.
Cleanup magic numbers.

So, this fixes oops.
Reported by Jim Westfall:
kernel: skb_over_panic: text:c0541fc7 len:1000 put:997 head:c166ac00 data:c166ac2f tail:0xc166b017 end:0xc166ac80 dev:eth0
kernel: ------------[ cut here ]------------
kernel: kernel BUG at net/core/skbuff.c:95!

Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/llc_pdu.h

@@ -381,7 +381,7 @@ static inline void llc_pdu_init_as_xid_cmd(struct sk_buff *skb,
 	xid_info->fmt_id = LLC_XID_FMT_ID;	/* 0x81 */
 	xid_info->type	 = svcs_supported;
 	xid_info->rw	 = rx_window << 1;	/* size of receive window */
-	skb_put(skb, 3);
+	skb_put(skb, sizeof(struct llc_xid_info));
 }
 
 /**
@@ -406,7 +406,7 @@ static inline void llc_pdu_init_as_xid_rsp(struct sk_buff *skb,
 	xid_info->fmt_id = LLC_XID_FMT_ID;
 	xid_info->type	 = svcs_supported;
 	xid_info->rw	 = rx_window << 1;
-	skb_put(skb, 3);
+	skb_put(skb, sizeof(struct llc_xid_info));
 }
 
 /* LLC Type 2 FRMR response information field format */

include/net/llc_sap.h

@@ -1,5 +1,8 @@
 #ifndef LLC_SAP_H
 #define LLC_SAP_H
+
+#include <asm/types.h>
+
 /*
  * Copyright (c) 1997 by Procom Technology,Inc.
  * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
@@ -19,8 +22,8 @@ struct sock;
 extern void llc_sap_rtn_pdu(struct llc_sap *sap, struct sk_buff *skb);
 extern void llc_save_primitive(struct sock *sk, struct sk_buff* skb,
 			       unsigned char prim);
-extern struct sk_buff *llc_alloc_frame(struct sock *sk,
-				       struct net_device *dev);
+extern struct sk_buff *llc_alloc_frame(struct sock *sk, struct net_device *dev,
+				       u8 type, u32 data_size);
 
 extern void llc_build_and_send_test_pkt(struct llc_sap *sap,
 				        struct sk_buff *skb,

net/llc/llc_c_ac.c

@@ -198,7 +198,7 @@ int llc_conn_ac_send_disc_cmd_p_set_x(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -223,7 +223,7 @@ int llc_conn_ac_send_dm_rsp_f_set_p(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -249,7 +249,7 @@ int llc_conn_ac_send_dm_rsp_f_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -282,7 +282,8 @@ int llc_conn_ac_send_frmr_rsp_f_set_x(struct sock *sk, struct sk_buff *skb)
 		llc_pdu_decode_pf_bit(skb, &f_bit);
 	else
 		f_bit = 0;
-	nskb = llc_alloc_frame(sk, llc->dev);
+	nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U,
+			       sizeof(struct llc_frmr_info));
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
 
@@ -306,7 +307,8 @@ int llc_conn_ac_resend_frmr_rsp_f_set_0(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U,
+					       sizeof(struct llc_frmr_info));
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -336,7 +338,8 @@ int llc_conn_ac_resend_frmr_rsp_f_set_p(struct sock *sk, struct sk_buff *skb)
 	struct llc_sock *llc = llc_sk(sk);
 
 	llc_pdu_decode_pf_bit(skb, &f_bit);
-	nskb = llc_alloc_frame(sk, llc->dev);
+	nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U,
+			       sizeof(struct llc_frmr_info));
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
 		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
@@ -424,7 +427,7 @@ int llc_conn_ac_resend_i_xxx_x_set_0_or_send_rr(struct sock *sk,
 	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -459,7 +462,7 @@ int llc_conn_ac_send_rej_cmd_p_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -483,7 +486,7 @@ int llc_conn_ac_send_rej_rsp_f_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -507,7 +510,7 @@ int llc_conn_ac_send_rej_xxx_x_set_0(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -531,7 +534,7 @@ int llc_conn_ac_send_rnr_cmd_p_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -555,7 +558,7 @@ int llc_conn_ac_send_rnr_rsp_f_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -579,7 +582,7 @@ int llc_conn_ac_send_rnr_xxx_x_set_0(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -615,7 +618,7 @@ int llc_conn_ac_opt_send_rnr_xxx_x_set_0(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -639,7 +642,7 @@ int llc_conn_ac_send_rr_cmd_p_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -663,7 +666,7 @@ int llc_conn_ac_send_rr_rsp_f_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -688,7 +691,7 @@ int llc_conn_ac_send_ack_rsp_f_set_1(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -712,7 +715,7 @@ int llc_conn_ac_send_rr_xxx_x_set_0(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -736,7 +739,7 @@ int llc_conn_ac_send_ack_xxx_x_set_0(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -770,7 +773,7 @@ int llc_conn_ac_send_sabme_cmd_p_set_x(struct sock *sk, struct sk_buff *skb)
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;
@@ -799,7 +802,7 @@ int llc_conn_ac_send_ua_rsp_f_set_p(struct sock *sk, struct sk_buff *skb)
 	u8 f_bit;
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_U, 0);
 
 	llc_pdu_decode_pf_bit(skb, &f_bit);
 	if (nskb) {
@@ -956,7 +959,7 @@ static int llc_conn_ac_send_rr_rsp_f_set_ackpf(struct sock *sk,
 {
 	int rc = -ENOBUFS;
 	struct llc_sock *llc = llc_sk(sk);
-	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev);
+	struct sk_buff *nskb = llc_alloc_frame(sk, llc->dev, LLC_PDU_TYPE_S, 0);
 
 	if (nskb) {
 		struct llc_sap *sap = llc->sap;

net/llc/llc_pdu.c

@@ -241,7 +241,7 @@ void llc_pdu_init_as_frmr_rsp(struct sk_buff *skb, struct llc_pdu_sn *prev_pdu,
 	FRMR_INFO_SET_PDU_INFO_2LONG_IND(frmr_info, vzyxw);
 	FRMR_INFO_SET_PDU_INVALID_Nr_IND(frmr_info, vzyxw);
 	FRMR_INFO_SET_PDU_INVALID_Ns_IND(frmr_info, vzyxw);
-	skb_put(skb, 5);
+	skb_put(skb, sizeof(struct llc_frmr_info));
 }
 
 /**

net/llc/llc_s_ac.c

@@ -103,7 +103,8 @@ int llc_sap_action_send_xid_r(struct llc_sap *sap, struct sk_buff *skb)
 	llc_pdu_decode_sa(skb, mac_da);
 	llc_pdu_decode_da(skb, mac_sa);
 	llc_pdu_decode_ssap(skb, &dsap);
-	nskb = llc_alloc_frame(NULL, skb->dev);
+	nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
+			       sizeof(struct llc_xid_info));
 	if (!nskb)
 		goto out;
 	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, sap->laddr.lsap, dsap,
@@ -144,11 +145,15 @@ int llc_sap_action_send_test_r(struct llc_sap *sap, struct sk_buff *skb)
 	u8 mac_da[ETH_ALEN], mac_sa[ETH_ALEN], dsap;
 	struct sk_buff *nskb;
 	int rc = 1;
+	u32 data_size;
 
 	llc_pdu_decode_sa(skb, mac_da);
 	llc_pdu_decode_da(skb, mac_sa);
 	llc_pdu_decode_ssap(skb, &dsap);
-	nskb = llc_alloc_frame(NULL, skb->dev);
+
+	/* The test request command is type U (llc_len = 3) */
+	data_size = ntohs(eth_hdr(skb)->h_proto) - 3;
+	nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U, data_size);
 	if (!nskb)
 		goto out;
 	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, sap->laddr.lsap, dsap,

net/llc/llc_sap.c

@@ -24,20 +24,41 @@
 #include <net/tcp_states.h>
 #include <linux/llc.h>
 
+static int llc_mac_header_len(unsigned short devtype)
+{
+	switch (devtype) {
+	case ARPHRD_ETHER:
+	case ARPHRD_LOOPBACK:
+		return sizeof(struct ethhdr);
+#ifdef CONFIG_TR
+	case ARPHRD_IEEE802_TR:
+		return sizeof(struct trh_hdr);
+#endif
+	}
+	return 0;
+}
+
 /**
  *	llc_alloc_frame - allocates sk_buff for frame
  *	@dev: network device this skb will be sent over
+ *	@type: pdu type to allocate
+ *	@data_size: data size to allocate
  *
  *	Allocates an sk_buff for frame and initializes sk_buff fields.
  *	Returns allocated skb or %NULL when out of memory.
  */
-struct sk_buff *llc_alloc_frame(struct sock *sk, struct net_device *dev)
+struct sk_buff *llc_alloc_frame(struct sock *sk, struct net_device *dev,
+				u8 type, u32 data_size)
 {
-	struct sk_buff *skb = alloc_skb(128, GFP_ATOMIC);
+	int hlen = type == LLC_PDU_TYPE_U ? 3 : 4;
+	struct sk_buff *skb;
+
+	hlen += llc_mac_header_len(dev->type);
+	skb = alloc_skb(hlen + data_size, GFP_ATOMIC);
 
 	if (skb) {
 		skb_reset_mac_header(skb);
-		skb_reserve(skb, 50);
+		skb_reserve(skb, hlen);
 		skb_reset_network_header(skb);
 		skb_reset_transport_header(skb);
 		skb->protocol = htons(ETH_P_802_2);

net/llc/llc_station.c

@@ -253,7 +253,8 @@ static int llc_station_ac_inc_xid_r_cnt_by_1(struct sk_buff *skb)
 static int llc_station_ac_send_null_dsap_xid_c(struct sk_buff *skb)
 {
 	int rc = 1;
-	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev);
+	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
+					       sizeof(struct llc_xid_info));
 
 	if (!nskb)
 		goto out;
@@ -274,7 +275,8 @@ static int llc_station_ac_send_xid_r(struct sk_buff *skb)
 {
 	u8 mac_da[ETH_ALEN], dsap;
 	int rc = 1;
-	struct sk_buff* nskb = llc_alloc_frame(NULL, skb->dev);
+	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
+					       sizeof(struct llc_xid_info));
 
 	if (!nskb)
 		goto out;
@@ -298,7 +300,12 @@ static int llc_station_ac_send_test_r(struct sk_buff *skb)
 {
 	u8 mac_da[ETH_ALEN], dsap;
 	int rc = 1;
-	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev);
+	u32 data_size;
+	struct sk_buff *nskb;
+
+	/* The test request command is type U (llc_len = 3) */
+	data_size = ntohs(eth_hdr(skb)->h_proto) - 3;
+	nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U, data_size);
 
 	if (!nskb)
 		goto out;