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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni CC: Kent Overstreet , Kuniyuki Iwashima , Kuniyuki Iwashima , Subject: [PATCH v4 net-next 08/11] af_unix: Define locking order for U_RECVQ_LOCK_EMBRYO in unix_collect_skb(). Date: Thu, 20 Jun 2024 13:56:20 -0700 Message-ID: <20240620205623.60139-9-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20240620205623.60139-1-kuniyu@amazon.com> References: <20240620205623.60139-1-kuniyu@amazon.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: EX19D033UWC004.ant.amazon.com (10.13.139.225) To EX19D004ANA001.ant.amazon.com (10.37.240.138) X-Patchwork-Delegate: kuba@kernel.org While GC is cleaning up cyclic references by SCM_RIGHTS, unix_collect_skb() collects skb in the socket's recvq. If the socket is TCP_LISTEN, we need to collect skb in the embryo's queue. Then, both the listener's recvq lock and the embroy's one are held. The locking is always done in the listener -> embryo order. Let's define it as unix_recvq_lock_cmp_fn() instead of using spin_lock_nested(). Note that the reverse order is defined for consistency. Signed-off-by: Kuniyuki Iwashima --- net/unix/af_unix.c | 21 +++++++++++++++++++++ net/unix/garbage.c | 8 +------- 2 files changed, 22 insertions(+), 7 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index a092d6999ae0..89675879038d 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -181,6 +181,25 @@ static int unix_state_lock_cmp_fn(const struct lockdep_map *_a, /* unix_state_double_lock(): ascending address order. */ return cmp_ptr(a, b); } + +static int unix_recvq_lock_cmp_fn(const struct lockdep_map *_a, + const struct lockdep_map *_b) +{ + const struct sock *a, *b; + + a = container_of(_a, struct sock, sk_receive_queue.lock.dep_map); + b = container_of(_b, struct sock, sk_receive_queue.lock.dep_map); + + /* unix_collect_skb(): listener -> embryo order. */ + if (a->sk_state == TCP_LISTEN && unix_sk(b)->listener == a) + return -1; + + /* Should never happen. Just to be symmetric. */ + if (b->sk_state == TCP_LISTEN && unix_sk(a)->listener == b) + return 1; + + return 0; +} #endif static unsigned int unix_unbound_hash(struct sock *sk) @@ -1028,6 +1047,8 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern, sk->sk_write_space = unix_write_space; sk->sk_max_ack_backlog = READ_ONCE(net->unx.sysctl_max_dgram_qlen); sk->sk_destruct = unix_sock_destructor; + lock_set_cmp_fn(&sk->sk_receive_queue.lock, unix_recvq_lock_cmp_fn, NULL); + u = unix_sk(sk); u->listener = NULL; u->vertex = NULL; diff --git a/net/unix/garbage.c b/net/unix/garbage.c index dfe94a90ece4..eb8aa5171a68 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -337,11 +337,6 @@ static bool unix_vertex_dead(struct unix_vertex *vertex) return true; } -enum unix_recv_queue_lock_class { - U_RECVQ_LOCK_NORMAL, - U_RECVQ_LOCK_EMBRYO, -}; - static void unix_collect_queue(struct unix_sock *u, struct sk_buff_head *hitlist) { skb_queue_splice_init(&u->sk.sk_receive_queue, hitlist); @@ -375,8 +370,7 @@ static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist skb_queue_walk(queue, skb) { struct sk_buff_head *embryo_queue = &skb->sk->sk_receive_queue; - /* listener -> embryo order, the inversion never happens. */ - spin_lock_nested(&embryo_queue->lock, U_RECVQ_LOCK_EMBRYO); + spin_lock(&embryo_queue->lock); unix_collect_queue(unix_sk(skb->sk), hitlist); spin_unlock(&embryo_queue->lock); }