[PATCH AUTOSEL 6.10 08/27] rtnetlink: move rtnl_lock handling out of af_netlink

Sasha Levin
2024-07-28T00:53:50Z

From: Jakub Kicinski <kuba@kernel.org>

[ Upstream commit 5380d64f8d766576ac5c0f627418b2d0e1d2641f ]

Now that we have an intermediate layer of code for handling
rtnl-level netlink dump quirks, we can move the rtnl_lock
taking there.

For dump handlers with RTNL_FLAG_DUMP_SPLIT_NLM_DONE we can
avoid taking rtnl_lock just to generate NLM_DONE, once again.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/rtnetlink.c | 9 +++++++--
net/netlink/af_netlink.c | 2 --
2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 4668d67180407..eabfc8290f5e2 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -6486,6 +6486,7 @@ static int rtnl_mdb_del(struct sk_buff *skb, struct nlmsghdr *nlh,

static int rtnl_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
{
+ const bool needs_lock = !(cb->flags & RTNL_FLAG_DUMP_UNLOCKED);
rtnl_dumpit_func dumpit = cb->data;
int err;

@@ -6495,7 +6496,11 @@ static int rtnl_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
if (!dumpit)
return 0;

+ if (needs_lock)
+ rtnl_lock();
err = dumpit(skb, cb);
+ if (needs_lock)
+ rtnl_unlock();

/* Old dump handlers used to send NLM_DONE as in a separate recvmsg().
* Some applications which parse netlink manually depend on this.
@@ -6515,7 +6520,8 @@ static int rtnetlink_dump_start(struct sock *ssk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *control)
{
- if (control->flags & RTNL_FLAG_DUMP_SPLIT_NLM_DONE) {
+ if (control->flags & RTNL_FLAG_DUMP_SPLIT_NLM_DONE ||
+ !(control->flags & RTNL_FLAG_DUMP_UNLOCKED)) {
WARN_ON(control->data);
control->data = control->dump;
control->dump = rtnl_dumpit;
@@ -6703,7 +6709,6 @@ static int __net_init rtnetlink_net_init(struct net *net)
struct netlink_kernel_cfg cfg = {
.groups = RTNLGRP_MAX,
.input = rtnetlink_rcv,
- .cb_mutex = &rtnl_mutex,
.flags = NL_CFG_F_NONROOT_RECV,
.bind = rtnetlink_bind,
};
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index fa9c090cf629e..8bbbe75e75dbe 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2330,8 +2330,6 @@ static int netlink_dump(struct sock *sk, bool lock_taken)

cb->extack = &extack;

- if (cb->flags & RTNL_FLAG_DUMP_UNLOCKED)
- extra_mutex = NULL;
if (extra_mutex)
mutex_lock(extra_mutex);
nlk->dump_done_errno = cb->dump(skb, cb);
--
2.43.0