1 files changed, 62 insertions, 9 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index fc232441cf23..c1564768000e 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1652,6 +1652,13 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
                         nlk->flags &= ~NETLINK_F_CAP_ACK;
                 err = 0;
                 break;
+        case NETLINK_EXT_ACK:
+                if (val)
+                        nlk->flags |= NETLINK_F_EXT_ACK;
+                else
+                        nlk->flags &= ~NETLINK_F_EXT_ACK;
+                err = 0;
+                break;
         default:
                 err = -ENOPROTOOPT;
         }
@@ -1736,6 +1743,15 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
                         return -EFAULT;
                 err = 0;
                 break;
+        case NETLINK_EXT_ACK:
+                if (len < sizeof(int))
+                        return -EINVAL;
+                len = sizeof(int);
+                val = nlk->flags & NETLINK_F_EXT_ACK ? 1 : 0;
+                if (put_user(len, optlen) || put_user(val, optval))
+                        return -EFAULT;
+                err = 0;
+                break;
         default:
                 err = -ENOPROTOOPT;
         }
@@ -2267,21 +2283,40 @@ error_free:
 }
 EXPORT_SYMBOL(__netlink_dump_start);
 
-void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
+void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
+                 const struct netlink_ext_ack *extack)
 {
         struct sk_buff *skb;
         struct nlmsghdr *rep;
         struct nlmsgerr *errmsg;
         size_t payload = sizeof(*errmsg);
+        size_t tlvlen = 0;
         struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk);
+        unsigned int flags = 0;
 
         /* Error messages get the original request appened, unless the user
-         * requests to cap the error message.
+         * requests to cap the error message, and get extra error data if
+         * requested.
          */
-        if (!(nlk->flags & NETLINK_F_CAP_ACK) && err)
-                payload += nlmsg_len(nlh);
+        if (err) {
+                if (!(nlk->flags & NETLINK_F_CAP_ACK))
+                        payload += nlmsg_len(nlh);
+                else
+                        flags |= NLM_F_CAPPED;
+                if (nlk->flags & NETLINK_F_EXT_ACK && extack) {
+                        if (extack->_msg)
+                                tlvlen += nla_total_size(strlen(extack->_msg) + 1);
+                        if (extack->bad_attr)
+                                tlvlen += nla_total_size(sizeof(u32));
+                }
+        } else {
+                flags |= NLM_F_CAPPED;
+        }
 
-        skb = nlmsg_new(payload, GFP_KERNEL);
+        if (tlvlen)
+                flags |= NLM_F_ACK_TLVS;
+
+        skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
         if (!skb) {
                 struct sock *sk;
 
@@ -2297,17 +2332,35 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
         }
 
         rep = __nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
-                          NLMSG_ERROR, payload, 0);
+                          NLMSG_ERROR, payload, flags);
         errmsg = nlmsg_data(rep);
         errmsg->error = err;
         memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
+
+        if (err && nlk->flags & NETLINK_F_EXT_ACK && extack) {
+                if (extack->_msg)
+                        WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
+                                               extack->_msg));
+                if (extack->bad_attr &&
+                    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
+                             (u8 *)extack->bad_attr >= in_skb->data +
+                                                       in_skb->len))
+                        WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
+                                            (u8 *)extack->bad_attr -
+                                            in_skb->data));
+        }
+
+        nlmsg_end(skb, rep);
+
         netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).portid, MSG_DONTWAIT);
 }
 EXPORT_SYMBOL(netlink_ack);
 
 int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
-                                                     struct nlmsghdr *))
+                                                   struct nlmsghdr *,
+                                                   struct netlink_ext_ack *))
 {
+        struct netlink_ext_ack extack = {};
         struct nlmsghdr *nlh;
         int err;
 
@@ -2328,13 +2381,13 @@ int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
                 if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
                         goto ack;
 
-                err = cb(skb, nlh);
+                err = cb(skb, nlh, &extack);
                 if (err == -EINTR)
                         goto skip;
 
 ack:
                 if (nlh->nlmsg_flags & NLM_F_ACK || err)
-                        netlink_ack(skb, nlh, err);
+                        netlink_ack(skb, nlh, err, &extack);
 
 skip:
                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);