[PATCH 4.19 38/88] netfilter: nfnetlink: nfnetlink_unicast() reports EAGAIN instead of ENOBUFS

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit ee921183557af39c1a0475f982d43b0fcac25e2e ]

Frontend callback reports EAGAIN to nfnetlink to retry a command, this
is used to signal that module autoloading is required. Unfortunately,
nlmsg_unicast() reports EAGAIN in case the receiver socket buffer gets
full, so it enters a busy-loop.

This patch updates nfnetlink_unicast() to turn EAGAIN into ENOBUFS and
to use nlmsg_unicast(). Remove the flags field in nfnetlink_unicast()
since this is always MSG_DONTWAIT in the existing code which is exactly
what nlmsg_unicast() passes to netlink_unicast() as parameter.

Fixes: 96518518cc41 ("netfilter: add nftables")
Reported-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/netfilter/nfnetlink.h |  3 +-
 net/netfilter/nf_tables_api.c       | 61 ++++++++++++++---------------
 net/netfilter/nfnetlink.c           | 11 ++++--
 net/netfilter/nfnetlink_log.c       |  3 +-
 net/netfilter/nfnetlink_queue.c     |  2 +-
 5 files changed, 40 insertions(+), 40 deletions(-)

diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index cf09ab37b45b7..e713476ff29db 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -43,8 +43,7 @@ int nfnetlink_has_listeners(struct net *net, unsigned int group);
 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 		   unsigned int group, int echo, gfp_t flags);
 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error);
-int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
-		      int flags);
+int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid);
 
 static inline u16 nfnl_msg_type(u8 subsys, u8 msg_type)
 {
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 159ec1533c980..5b4632826dc66 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -718,11 +718,11 @@ static int nf_tables_gettable(struct net *net, struct sock *nlsk,
 					nlh->nlmsg_seq, NFT_MSG_NEWTABLE, 0,
 					family, table);
 	if (err < 0)
-		goto err;
+		goto err_fill_table_info;
 
-	return nlmsg_unicast(nlsk, skb2, NETLINK_CB(skb).portid);
+	return nfnetlink_unicast(skb2, net, NETLINK_CB(skb).portid);
 
-err:
+err_fill_table_info:
 	kfree_skb(skb2);
 	return err;
 }
@@ -1383,11 +1383,11 @@ static int nf_tables_getchain(struct net *net, struct sock *nlsk,
 					nlh->nlmsg_seq, NFT_MSG_NEWCHAIN, 0,
 					family, table, chain);
 	if (err < 0)
-		goto err;
+		goto err_fill_chain_info;
 
-	return nlmsg_unicast(nlsk, skb2, NETLINK_CB(skb).portid);
+	return nfnetlink_unicast(skb2, net, NETLINK_CB(skb).portid);
 
-err:
+err_fill_chain_info:
 	kfree_skb(skb2);
 	return err;
 }
@@ -2488,11 +2488,11 @@ static int nf_tables_getrule(struct net *net, struct sock *nlsk,
 				       nlh->nlmsg_seq, NFT_MSG_NEWRULE, 0,
 				       family, table, chain, rule);
 	if (err < 0)
-		goto err;
+		goto err_fill_rule_info;
 
-	return nlmsg_unicast(nlsk, skb2, NETLINK_CB(skb).portid);
+	return nfnetlink_unicast(skb2, net, NETLINK_CB(skb).portid);
 
-err:
+err_fill_rule_info:
 	kfree_skb(skb2);
 	return err;
 }
@@ -3377,11 +3377,11 @@ static int nf_tables_getset(struct net *net, struct sock *nlsk,
 
 	err = nf_tables_fill_set(skb2, &ctx, set, NFT_MSG_NEWSET, 0);
 	if (err < 0)
-		goto err;
+		goto err_fill_set_info;
 
-	return nlmsg_unicast(nlsk, skb2, NETLINK_CB(skb).portid);
+	return nfnetlink_unicast(skb2, net, NETLINK_CB(skb).portid);
 
-err:
+err_fill_set_info:
 	kfree_skb(skb2);
 	return err;
 }
@@ -4157,24 +4157,18 @@ static int nft_get_set_elem(struct nft_ctx *ctx, struct nft_set *set,
 	err = -ENOMEM;
 	skb = nlmsg_new(NLMSG_GOODSIZE, GFP_ATOMIC);
 	if (skb == NULL)
-		goto err1;
+		return err;
 
 	err = nf_tables_fill_setelem_info(skb, ctx, ctx->seq, ctx->portid,
 					  NFT_MSG_NEWSETELEM, 0, set, &elem);
 	if (err < 0)
-		goto err2;
+		goto err_fill_setelem;
 
-	err = nfnetlink_unicast(skb, ctx->net, ctx->portid, MSG_DONTWAIT);
-	/* This avoids a loop in nfnetlink. */
-	if (err < 0)
-		goto err1;
+	return nfnetlink_unicast(skb, ctx->net, ctx->portid);
 
-	return 0;
-err2:
+err_fill_setelem:
 	kfree_skb(skb);
-err1:
-	/* this avoids a loop in nfnetlink. */
-	return err == -EAGAIN ? -ENOBUFS : err;
+	return err;
 }
 
 /* called with rcu_read_lock held */
@@ -5273,10 +5267,11 @@ static int nf_tables_getobj(struct net *net, struct sock *nlsk,
 				      nlh->nlmsg_seq, NFT_MSG_NEWOBJ, 0,
 				      family, table, obj, reset);
 	if (err < 0)
-		goto err;
+		goto err_fill_obj_info;
 
-	return nlmsg_unicast(nlsk, skb2, NETLINK_CB(skb).portid);
-err:
+	return nfnetlink_unicast(skb2, net, NETLINK_CB(skb).portid);
+
+err_fill_obj_info:
 	kfree_skb(skb2);
 	return err;
 }
@@ -5933,10 +5928,11 @@ static int nf_tables_getflowtable(struct net *net, struct sock *nlsk,
 					    NFT_MSG_NEWFLOWTABLE, 0, family,
 					    flowtable);
 	if (err < 0)
-		goto err;
+		goto err_fill_flowtable_info;
 
-	return nlmsg_unicast(nlsk, skb2, NETLINK_CB(skb).portid);
-err:
+	return nfnetlink_unicast(skb2, net, NETLINK_CB(skb).portid);
+
+err_fill_flowtable_info:
 	kfree_skb(skb2);
 	return err;
 }
@@ -6097,10 +6093,11 @@ static int nf_tables_getgen(struct net *net, struct sock *nlsk,
 	err = nf_tables_fill_gen_info(skb2, net, NETLINK_CB(skb).portid,
 				      nlh->nlmsg_seq);
 	if (err < 0)
-		goto err;
+		goto err_fill_gen_info;
 
-	return nlmsg_unicast(nlsk, skb2, NETLINK_CB(skb).portid);
-err:
+	return nfnetlink_unicast(skb2, net, NETLINK_CB(skb).portid);
+
+err_fill_gen_info:
 	kfree_skb(skb2);
 	return err;
 }
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 7f2c1915763f8..9bacddc761ba4 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -148,10 +148,15 @@ int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
 }
 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 
-int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
-		      int flags)
+int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid)
 {
-	return netlink_unicast(net->nfnl, skb, portid, flags);
+	int err;
+
+	err = nlmsg_unicast(net->nfnl, skb, portid);
+	if (err == -EAGAIN)
+		err = -ENOBUFS;
+
+	return err;
 }
 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 
diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 332c69d27b478..25298b3eb8546 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -359,8 +359,7 @@ __nfulnl_send(struct nfulnl_instance *inst)
 			goto out;
 		}
 	}
-	nfnetlink_unicast(inst->skb, inst->net, inst->peer_portid,
-			  MSG_DONTWAIT);
+	nfnetlink_unicast(inst->skb, inst->net, inst->peer_portid);
 out:
 	inst->qlen = 0;
 	inst->skb = NULL;
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index d33094f4ec41e..f81a3ce0fe48e 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -685,7 +685,7 @@ __nfqnl_enqueue_packet(struct net *net, struct nfqnl_instance *queue,
 	*packet_id_ptr = htonl(entry->id);
 
 	/* nfnetlink_unicast will either free the nskb or add it to a socket */
-	err = nfnetlink_unicast(nskb, net, queue->peer_portid, MSG_DONTWAIT);
+	err = nfnetlink_unicast(nskb, net, queue->peer_portid);
 	if (err < 0) {
 		if (queue->flags & NFQA_CFG_F_FAIL_OPEN) {
 			failopen = 1;
-- 
2.25.1