genetlink: fix genlmsg_nlhdr()

According to the description, first argument of genlmsg_nlhdr() points to
what genlmsg_put() returns, i.e. beginning of user header. Therefore we
should only subtract size of genetlink header and netlink message header,
not user header.

This also means we don't need to pass the pointer to genetlink family and
the same is true for genl_dump_check_consistent() which is the only caller
of genlmsg_nlhdr(). (Note that at the moment, these functions are only
used for families which do not have user header so that they are not
affected.)

Fixes: 670dc283 ("netlink: advertise incomplete dumps")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macsec.c

@@ -2411,7 +2411,7 @@ static int dump_secy(struct macsec_secy *secy, struct net_device *dev,
 	if (!hdr)
 		return -EMSGSIZE;
 
-	genl_dump_check_consistent(cb, hdr, &macsec_fam);
+	genl_dump_check_consistent(cb, hdr);
 
 	if (nla_put_u32(skb, MACSEC_ATTR_IFINDEX, dev->ifindex))
 		goto nla_put_failure;

drivers/net/wireless/mac80211_hwsim.c

@@ -2805,7 +2805,7 @@ static int mac80211_hwsim_get_radio(struct sk_buff *skb,
 		return -EMSGSIZE;
 
 	if (cb)
-		genl_dump_check_consistent(cb, hdr, &hwsim_genl_family);
+		genl_dump_check_consistent(cb, hdr);
 
 	if (data->alpha2[0] && data->alpha2[1])
 		param.reg_alpha2 = data->alpha2;

include/net/genetlink.h

@@ -154,15 +154,12 @@ void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
 /**
  * genlmsg_nlhdr - Obtain netlink header from user specified header
  * @user_hdr: user header as returned from genlmsg_put()
- * @family: generic netlink family
  *
  * Returns pointer to netlink header.
  */
-static inline struct nlmsghdr *
-genlmsg_nlhdr(void *user_hdr, const struct genl_family *family)
+static inline struct nlmsghdr *genlmsg_nlhdr(void *user_hdr)
 {
 	return (struct nlmsghdr *)((char *)user_hdr -
-				   family->hdrsize -
 				   GENL_HDRLEN -
 				   NLMSG_HDRLEN);
 }
@@ -190,16 +187,14 @@ static inline int genlmsg_parse(const struct nlmsghdr *nlh,
  * genl_dump_check_consistent - check if sequence is consistent and advertise if not
  * @cb: netlink callback structure that stores the sequence number
  * @user_hdr: user header as returned from genlmsg_put()
- * @family: generic netlink family
  *
  * Cf. nl_dump_check_consistent(), this just provides a wrapper to make it
  * simpler to use with generic netlink.
  */
 static inline void genl_dump_check_consistent(struct netlink_callback *cb,
-					      void *user_hdr,
-					      const struct genl_family *family)
+					      void *user_hdr)
 {
-	nl_dump_check_consistent(cb, genlmsg_nlhdr(user_hdr, family));
+	nl_dump_check_consistent(cb, genlmsg_nlhdr(user_hdr));
 }
 
 /**

net/nfc/netlink.c

@@ -75,7 +75,7 @@ static int nfc_genl_send_target(struct sk_buff *msg, struct nfc_target *target,
 	if (!hdr)
 		return -EMSGSIZE;
 
-	genl_dump_check_consistent(cb, hdr, &nfc_genl_family);
+	genl_dump_check_consistent(cb, hdr);
 
 	if (nla_put_u32(msg, NFC_ATTR_TARGET_INDEX, target->idx) ||
 	    nla_put_u32(msg, NFC_ATTR_PROTOCOLS, target->supported_protocols) ||
@@ -603,7 +603,7 @@ static int nfc_genl_send_device(struct sk_buff *msg, struct nfc_dev *dev,
 		return -EMSGSIZE;
 
 	if (cb)
-		genl_dump_check_consistent(cb, hdr, &nfc_genl_family);
+		genl_dump_check_consistent(cb, hdr);
 
 	if (nfc_genl_setup_device_added(dev, msg))
 		goto nla_put_failure;
@@ -1356,7 +1356,7 @@ static int nfc_genl_send_se(struct sk_buff *msg, struct nfc_dev *dev,
 			goto nla_put_failure;
 
 		if (cb)
-			genl_dump_check_consistent(cb, hdr, &nfc_genl_family);
+			genl_dump_check_consistent(cb, hdr);
 
 		if (nla_put_u32(msg, NFC_ATTR_DEVICE_INDEX, dev->idx) ||
 		    nla_put_u32(msg, NFC_ATTR_SE_INDEX, se->idx) ||

net/wireless/nl80211.c

@@ -6291,7 +6291,7 @@ static int nl80211_send_regdom(struct sk_buff *msg, struct netlink_callback *cb,
 	if (!hdr)
 		return -1;
 
-	genl_dump_check_consistent(cb, hdr, &nl80211_fam);
+	genl_dump_check_consistent(cb, hdr);
 
 	if (nl80211_put_regdom(regdom, msg))
 		goto nla_put_failure;
@@ -7722,7 +7722,7 @@ static int nl80211_send_bss(struct sk_buff *msg, struct netlink_callback *cb,
 	if (!hdr)
 		return -1;
 
-	genl_dump_check_consistent(cb, hdr, &nl80211_fam);
+	genl_dump_check_consistent(cb, hdr);
 
 	if (nla_put_u32(msg, NL80211_ATTR_GENERATION, rdev->bss_generation))
 		goto nla_put_failure;