[PATCH 6.6 16/50] Revert "mptcp: add needs_id for netlink appending addr"

Greg Kroah-Hartman
2026-04-13T16:14:09Z

From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>

[ Upstream commit 8e2760eaab778494fc1fa257031e0e1799647f46 ]

This commit was originally adding the ability to add MPTCP endpoints
with ID 0 by accident. The in-kernel PM, handling MPTCP endpoints at the
net namespace level, is not supposed to handle endpoints with such ID,
because this ID 0 is reserved to the initial subflow, as mentioned in
the MPTCPv1 protocol [1], a per-connection setting.

Note that 'ip mptcp endpoint add id 0' stops early with an error, but
other tools might still request the in-kernel PM to create MPTCP
endpoints with this restricted ID 0.

In other words, it was wrong to call the mptcp_pm_has_addr_attr_id
helper to check whether the address ID attribute is set: if it was set
to 0, a new MPTCP endpoint would be created with ID 0, which is not
expected, and might cause various issues later.

Fixes: 584f38942626 ("mptcp: add needs_id for netlink appending addr")
Cc: stable@vger.kernel.org
Link: https://datatracker.ietf.org/doc/html/rfc8684#section-3.2-9 [1]
Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260407-net-mptcp-revert-pm-needs-id-v2-1-7a25cbc324f8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ applied changes to net/mptcp/pm_netlink.c instead of renamed net/mptcp/pm_kernel.c ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mptcp/pm_netlink.c | 24 +++++-------------------
1 file changed, 5 insertions(+), 19 deletions(-)

--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -1079,7 +1079,7 @@ static void __mptcp_pm_release_addr_entr

static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
struct mptcp_pm_addr_entry *entry,
- bool needs_id, bool replace)
+ bool replace)
{
struct mptcp_pm_addr_entry *cur, *del_entry = NULL;
unsigned int addr_max;
@@ -1138,7 +1138,7 @@ static int mptcp_pm_nl_append_new_local_
}
}

- if (!entry->addr.id && needs_id) {
+ if (!entry->addr.id) {
find_next:
entry->addr.id = find_next_zero_bit(pernet->id_bitmap,
MPTCP_PM_MAX_ADDR_ID + 1,
@@ -1149,7 +1149,7 @@ find_next:
}
}

- if (!entry->addr.id && needs_id)
+ if (!entry->addr.id)
goto out;

__set_bit(entry->addr.id, pernet->id_bitmap);
@@ -1282,7 +1282,7 @@ int mptcp_pm_nl_get_local_id(struct mptc
entry->ifindex = 0;
entry->flags = MPTCP_PM_ADDR_FLAG_IMPLICIT;
entry->lsk = NULL;
- ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, true, false);
+ ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, false);
if (ret < 0)
kfree(entry);

@@ -1524,18 +1524,6 @@ next:
return 0;
}

-static bool mptcp_pm_has_addr_attr_id(const struct nlattr *attr,
- struct genl_info *info)
-{
- struct nlattr *tb[MPTCP_PM_ADDR_ATTR_MAX + 1];
-
- if (!nla_parse_nested_deprecated(tb, MPTCP_PM_ADDR_ATTR_MAX, attr,
- mptcp_pm_addr_policy, info->extack) &&
- tb[MPTCP_PM_ADDR_ATTR_ID])
- return true;
- return false;
-}
-
static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
{
struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
@@ -1577,9 +1565,7 @@ static int mptcp_nl_cmd_add_addr(struct
goto out_free;
}
}
- ret = mptcp_pm_nl_append_new_local_addr(pernet, entry,
- !mptcp_pm_has_addr_attr_id(attr, info),
- true);
+ ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, true);
if (ret < 0) {
GENL_SET_ERR_MSG_FMT(info, "too many addresses or duplicate one: %d", ret);
goto out_free;