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

Greg Kroah-Hartman
2020-09-08T18:38:15Z

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