From 561f3a8f930cf2e44f493fa04d932ba9a2362cc5 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Mon, 3 May 2021 16:31:25 +0200
Subject: wg_noise: set handshake to dead before removing keypair

Otherwise CK_LIST_REMOVE might be called twice on the same element.
Running the following trigger will reproduce the bug that Manojav
reported:

    #!/usr/local/bin/bash
    NUM_PEER=50
    peer_args=( )
    for ((i=0; i<NUM_PEER; i++)); do
      port="$RANDOM"
      private="$(wg genkey)"
      ifconfig "wg$i" create
      wg set "wg$i" listen-port "$port" private-key <(echo "$private")
      peer_args+=( peer "$(wg pubkey <<<"$private")" endpoint "127.0.0.1:$port" persistent-keepalive 1 )
    done
    for ((i=0; i<NUM_PEER; i++)); do
      wg set "wg$i" "${peer_args[@]}"
      ifconfig "wg$i" up
    done
    wg
    while true; do
      for ((i=0; i<NUM_PEER; i++)); do
        ifconfig "wg$i" down
        ifconfig "wg$i" up
      done
    done

Reported-by: Manojav Sridhar <manojav@manojav.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 src/wg_noise.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/wg_noise.c b/src/wg_noise.c
index cb9f525..41f7f50 100644
--- a/src/wg_noise.c
+++ b/src/wg_noise.c
@@ -445,9 +445,9 @@ noise_remote_index_remove(struct noise_local *l, struct noise_remote *r)
 	rw_assert(&r->r_handshake_lock, RA_WLOCKED);
 	if (r->r_handshake_state != HANDSHAKE_DEAD) {
 		rw_wlock(&l->l_index_lock);
+		r->r_handshake_state = HANDSHAKE_DEAD;
 		CK_LIST_REMOVE(&r->r_index, i_entry);
 		rw_wunlock(&l->l_index_lock);
-		r->r_handshake_state = HANDSHAKE_DEAD;
 		return (1);
 	}
 	return (0);
@@ -634,6 +634,7 @@ noise_add_new_keypair(struct noise_local *l, struct noise_remote *r,
 
 	rw_wlock(&l->l_index_lock);
 	CK_LIST_INSERT_BEFORE(r_i, &kp->kp_index, i_entry);
+	r->r_handshake_state = HANDSHAKE_DEAD;
 	CK_LIST_REMOVE(r_i, i_entry);
 	rw_wunlock(&l->l_index_lock);
 
@@ -1346,7 +1347,7 @@ noise_tai64n_now(uint8_t output[NOISE_TIMESTAMP_LEN])
 	memcpy(output + sizeof(sec), &nsec, sizeof(nsec));
 }
 
-static __inline int
+static inline int
 noise_timer_expired(sbintime_t timer, uint32_t sec, uint32_t nsec)
 {
 	sbintime_t now = getsbinuptime();
-- 
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