[PATCH net 0/3] mptcp: pm: a few more fixes

[PATCH net 0/3] mptcp: pm: a few more fixes

[Matthieu Baerts (NGI0)]

Three small fixes related to the MPTCP path-manager:

- Patch 1: correctly reflect the backup flag to the corresponding local
  address entry of the userspace path-manager. A fix for v5.19.

- Patch 2: hold the PM lock when deleting an entry from the local
  addresses of the userspace path-manager to avoid messing up with this
  list. A fix for v5.19.

- Patch 3: use _rcu variant to iterate the in-kernel path-manager's
  local addresses list, when under rcu_read_lock(). A fix for v5.17.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Geliang Tang (2):
      mptcp: update local address flags when setting it
      mptcp: hold pm lock when deleting entry

Matthieu Baerts (NGI0) (1):
      mptcp: pm: use _rcu variant under rcu_read_lock

 net/mptcp/pm_netlink.c   |  3 ++-
 net/mptcp/pm_userspace.c | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
---
base-commit: 20bbe5b802494444791beaf2c6b9597fcc67ff49
change-id: 20241112-net-mptcp-misc-6-12-pm-97ea0ec1d979

Best regards,
-- 
Matthieu Baerts (NGI0) <matttbe@kernel.org>

[PATCH net 1/3] mptcp: update local address flags when setting it

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

Just like in-kernel pm, when userspace pm does set_flags, it needs to send
out MP_PRIO signal, and also modify the flags of the corresponding address
entry in the local address list. This patch implements the missing logic.

Traverse all address entries on userspace_pm_local_addr_list to find the
local address entry, if bkup is true, set the flags of this entry with
FLAG_BACKUP, otherwise, clear FLAG_BACKUP.

Fixes: 892f396c8e68 ("mptcp: netlink: issue MP_PRIO signals from userspace PMs")
Cc: stable@vger.kernel.org
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_userspace.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index 56dfea9862b7b24dd0eaa8bbedcf22a7f6829ccf..3f888bfe1462ee3c75a3fb6eefe29cb712471410 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -560,6 +560,7 @@ int mptcp_userspace_pm_set_flags(struct sk_buff *skb, struct genl_info *info)
 	struct nlattr *token = info->attrs[MPTCP_PM_ATTR_TOKEN];
 	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
 	struct net *net = sock_net(skb->sk);
+	struct mptcp_pm_addr_entry *entry;
 	struct mptcp_sock *msk;
 	int ret = -EINVAL;
 	struct sock *sk;
@@ -601,6 +602,17 @@ int mptcp_userspace_pm_set_flags(struct sk_buff *skb, struct genl_info *info)
 	if (loc.flags & MPTCP_PM_ADDR_FLAG_BACKUP)
 		bkup = 1;
 
+	spin_lock_bh(&msk->pm.lock);
+	list_for_each_entry(entry, &msk->pm.userspace_pm_local_addr_list, list) {
+		if (mptcp_addresses_equal(&entry->addr, &loc.addr, false)) {
+			if (bkup)
+				entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+			else
+				entry->flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
+		}
+	}
+	spin_unlock_bh(&msk->pm.lock);
+
 	lock_sock(sk);
 	ret = mptcp_pm_nl_mp_prio_send_ack(msk, &loc.addr, &rem.addr, bkup);
 	release_sock(sk);

-- 
2.45.2

[PATCH net 2/3] mptcp: hold pm lock when deleting entry

[Matthieu Baerts (NGI0)]

From: Geliang Tang <tanggeliang@kylinos.cn>

When traversing userspace_pm_local_addr_list and deleting an entry from
it in mptcp_pm_nl_remove_doit(), msk->pm.lock should be held.

This patch holds this lock before mptcp_userspace_pm_lookup_addr_by_id()
and releases it after list_move() in mptcp_pm_nl_remove_doit().

Fixes: d9a4594edabf ("mptcp: netlink: Add MPTCP_PM_CMD_REMOVE")
Cc: stable@vger.kernel.org
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_userspace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index 3f888bfe1462ee3c75a3fb6eefe29cb712471410..e35178f5205faac4a9199df1ffca79085e4b7c68 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -308,14 +308,17 @@ int mptcp_pm_nl_remove_doit(struct sk_buff *skb, struct genl_info *info)
 
 	lock_sock(sk);
 
+	spin_lock_bh(&msk->pm.lock);
 	match = mptcp_userspace_pm_lookup_addr_by_id(msk, id_val);
 	if (!match) {
 		GENL_SET_ERR_MSG(info, "address with specified id not found");
+		spin_unlock_bh(&msk->pm.lock);
 		release_sock(sk);
 		goto out;
 	}
 
 	list_move(&match->list, &free_list);
+	spin_unlock_bh(&msk->pm.lock);
 
 	mptcp_pm_remove_addrs(msk, &free_list);
 

-- 
2.45.2

[PATCH net 3/3] mptcp: pm: use _rcu variant under rcu_read_lock

[Matthieu Baerts (NGI0)]

In mptcp_pm_create_subflow_or_signal_addr(), rcu_read_(un)lock() are
used as expected to iterate over the list of local addresses, but
list_for_each_entry() was used instead of list_for_each_entry_rcu() in
__lookup_addr(). It is important to use this variant which adds the
required READ_ONCE() (and diagnostic checks if enabled).

Because __lookup_addr() is also used in mptcp_pm_nl_set_flags() where it
is called under the pernet->lock and not rcu_read_lock(), an extra
condition is then passed to help the diagnostic checks making sure
either the associated spin lock or the RCU lock is held.

Fixes: 86e39e04482b ("mptcp: keep track of local endpoint still available for each msk")
Cc: stable@vger.kernel.org
Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/pm_netlink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index db586a5b3866f66a24431d7f2cab566f89102885..45a2b5f05d38b0e7f334578f5ee6923a8ff8f7b2 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -524,7 +524,8 @@ __lookup_addr(struct pm_nl_pernet *pernet, const struct mptcp_addr_info *info)
 {
 	struct mptcp_pm_addr_entry *entry;
 
-	list_for_each_entry(entry, &pernet->local_addr_list, list) {
+	list_for_each_entry_rcu(entry, &pernet->local_addr_list, list,
+				lockdep_is_held(&pernet->lock)) {
 		if (mptcp_addresses_equal(&entry->addr, info, entry->addr.port))
 			return entry;
 	}

-- 
2.45.2

Re: [PATCH net 0/3] mptcp: pm: a few more fixes

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 12 Nov 2024 20:18:32 +0100 you wrote:
> Three small fixes related to the MPTCP path-manager:
> 
> - Patch 1: correctly reflect the backup flag to the corresponding local
>   address entry of the userspace path-manager. A fix for v5.19.
> 
> - Patch 2: hold the PM lock when deleting an entry from the local
>   addresses of the userspace path-manager to avoid messing up with this
>   list. A fix for v5.19.
> 
> [...]

Here is the summary with links:
  - [net,1/3] mptcp: update local address flags when setting it
    https://git.kernel.org/netdev/net/c/e0266319413d
  - [net,2/3] mptcp: hold pm lock when deleting entry
    https://git.kernel.org/netdev/net/c/f642c5c4d528
  - [net,3/3] mptcp: pm: use _rcu variant under rcu_read_lock
    https://git.kernel.org/netdev/net/c/db3eab8110bc

You are awesome, thank you!
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