[PATCH 5.15 035/110] mptcp: fix msk traversal in mptcp_nl_cmd_set_flags()

Greg Kroah-Hartman
2022-02-07T11:48:44Z

From: Paolo Abeni <pabeni@redhat.com>

commit 8e9eacad7ec7a9cbf262649ebf1fa6e6f6cc7d82 upstream.

The MPTCP endpoint list is under RCU protection, guarded by the
pernet spinlock. mptcp_nl_cmd_set_flags() traverses the list
without acquiring the spin-lock nor under the RCU critical section.

This change addresses the issue performing the lookup and the endpoint
update under the pernet spinlock.

[The upstream commit had to handle a lookup_by_id variable that is only
present in 5.17. This version of the patch removes that variable, so
the __lookup_addr() function only handles the lookup as it is
implemented in 5.15 and 5.16. It also removes one 'const' keyword to
prevent a warning due to differing const-ness in the 5.17 version of
addresses_equal().]

Fixes: 0f9f696a502e ("mptcp: add set_flags command in PM netlink")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mptcp/pm_netlink.c | 34 +++++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)

--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -459,6 +459,18 @@ static unsigned int fill_remote_addresse
return i;
}

+static struct mptcp_pm_addr_entry *
+__lookup_addr(struct pm_nl_pernet *pernet, struct mptcp_addr_info *info)
+{
+ struct mptcp_pm_addr_entry *entry;
+
+ list_for_each_entry(entry, &pernet->local_addr_list, list) {
+ if (addresses_equal(&entry->addr, info, true))
+ return entry;
+ }
+ return NULL;
+}
+
static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
{
struct sock *sk = (struct sock *)msk;
@@ -1725,17 +1737,21 @@ static int mptcp_nl_cmd_set_flags(struct
if (addr.flags & MPTCP_PM_ADDR_FLAG_BACKUP)
bkup = 1;

- list_for_each_entry(entry, &pernet->local_addr_list, list) {
- if (addresses_equal(&entry->addr, &addr.addr, true)) {
- mptcp_nl_addr_backup(net, &entry->addr, bkup);
-
- if (bkup)
- entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
- else
- entry->flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
- }
+ spin_lock_bh(&pernet->lock);
+ entry = __lookup_addr(pernet, &addr.addr);
+ if (!entry) {
+ spin_unlock_bh(&pernet->lock);
+ return -EINVAL;
}

+ if (bkup)
+ entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+ else
+ entry->flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
+ addr = *entry;
+ spin_unlock_bh(&pernet->lock);
+
+ mptcp_nl_addr_backup(net, &addr.addr, bkup);
return 0;
}