git: 394d701c41ec - stable/15 - if_ovpn: use epoch to free peers

The branch stable/15 has been updated by kp:

URL: https://cgit.FreeBSD.org/src/commit/?id=394d701c41ec567cbb5ddaeeb5f718ea39cb9024

commit 394d701c41ec567cbb5ddaeeb5f718ea39cb9024
Author:     Kristof Provost <kp@FreeBSD.org>
AuthorDate: 2025-12-09 10:55:30 +0000
Commit:     Kristof Provost <kp@FreeBSD.org>
CommitDate: 2025-12-17 09:23:03 +0000

    if_ovpn: use epoch to free peers
    
    Avoid a possible use-after-free in the rx path.
    ovpn_decrypt_rx_cb() calls ovpn_finish_rx() which releases the lock,
    but continues to use the peer.
    Ensure that the peer cannot be freed until we're sure all potential
    users have stopped using it (i.e. have left net_epoch).
    
    Reported by:    Kevin Day <kevin@your.org>
    MFC after:      1 week
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    
    (cherry picked from commit 5e2bbfe387f7eac8f802c4b6ad2114f0e17bb5f2)
---
 sys/net/if_ovpn.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/sys/net/if_ovpn.c b/sys/net/if_ovpn.c
index 8ce3491d072e..5be05667857b 100644
--- a/sys/net/if_ovpn.c
+++ b/sys/net/if_ovpn.c
@@ -161,6 +161,7 @@ struct ovpn_kpeer {
 	struct callout		 ping_rcv;
 
 	counter_u64_t		 counters[OVPN_PEER_COUNTER_SIZE];
+	struct epoch_context	 epoch_ctx;
 };
 
 struct ovpn_counters {
@@ -568,6 +569,15 @@ ovpn_notify_float(struct ovpn_softc *sc, uint32_t peerid,
 	return (0);
 }
 
+static void
+_ovpn_free_peer(struct epoch_context *ctx) {
+	struct ovpn_kpeer *peer = __containerof(ctx, struct ovpn_kpeer,
+	    epoch_ctx);
+
+	uma_zfree_pcpu(pcpu_zone_4, peer->last_active);
+	free(peer, M_OVPN);
+}
+
 static void
 ovpn_peer_release_ref(struct ovpn_kpeer *peer, bool locked)
 {
@@ -606,8 +616,8 @@ ovpn_peer_release_ref(struct ovpn_kpeer *peer, bool locked)
 
 	callout_stop(&peer->ping_send);
 	callout_stop(&peer->ping_rcv);
-	uma_zfree_pcpu(pcpu_zone_4, peer->last_active);
-	free(peer, M_OVPN);
+
+	NET_EPOCH_CALL(_ovpn_free_peer, &peer->epoch_ctx);
 
 	if (! locked)
 		OVPN_WUNLOCK(sc);