From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 086601863 for ; Wed, 28 Dec 2022 15:45:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82C94C433D2; Wed, 28 Dec 2022 15:45:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1672242330; bh=gaX2EA+0i5+uWOb8V/ekuvtOzAQeu4uTFtlGJmSCzm4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gYnSK/Ui4jTEDO4unGgB/HzY82LU1WmBF+CX56ALn2sENlnyllqyr3TUCVYv1Cvkn Dj2VuDYLIdbtI4MNvV8SlE0UtI1Qn6FugfhKEL01c4sjVwh1r8z3+ygYHYVUb+Isv1 w5oo54NOX6ZleevufdS2fX8PmHG7BwxgcaijvRSI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kirill Tkhai , Paolo Abeni , Sasha Levin Subject: [PATCH 5.15 591/731] unix: Fix race in SOCK_SEQPACKETs unix_dgram_sendmsg() Date: Wed, 28 Dec 2022 15:41:38 +0100 Message-Id: <20221228144313.674498074@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20221228144256.536395940@linuxfoundation.org> References: <20221228144256.536395940@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Kirill Tkhai [ Upstream commit 3ff8bff704f4de125dca2262e5b5b963a3da1d87 ] There is a race resulting in alive SOCK_SEQPACKET socket may change its state from TCP_ESTABLISHED to TCP_CLOSE: unix_release_sock(peer) unix_dgram_sendmsg(sk) sock_orphan(peer) sock_set_flag(peer, SOCK_DEAD) sock_alloc_send_pskb() if !(sk->sk_shutdown & SEND_SHUTDOWN) OK if sock_flag(peer, SOCK_DEAD) sk->sk_state = TCP_CLOSE sk->sk_shutdown = SHUTDOWN_MASK After that socket sk remains almost normal: it is able to connect, listen, accept and recvmsg, while it can't sendmsg. Since this is the only possibility for alive SOCK_SEQPACKET to change the state in such way, we should better fix this strange and potentially danger corner case. Note, that we will return EPIPE here like this is normally done in sock_alloc_send_pskb(). Originally used ECONNREFUSED looks strange, since it's strange to return a specific retval in dependence of race in kernel, when user can't affect on this. Also, move TCP_CLOSE assignment for SOCK_DGRAM sockets under state lock to fix race with unix_dgram_connect(): unix_dgram_connect(other) unix_dgram_sendmsg(sk) unix_peer(sk) = NULL unix_state_unlock(sk) unix_state_double_lock(sk, other) sk->sk_state = TCP_ESTABLISHED unix_peer(sk) = other unix_state_double_unlock(sk, other) sk->sk_state = TCP_CLOSED This patch fixes both of these races. Fixes: 83301b5367a9 ("af_unix: Set TCP_ESTABLISHED for datagram sockets too") Signed-off-by: Kirill Tkhai Link: https://lore.kernel.org/r/135fda25-22d5-837a-782b-ceee50e19844@ya.ru Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/unix/af_unix.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 545823c1d5ed..0a59a00cb581 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1865,13 +1865,20 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg, unix_state_lock(sk); err = 0; - if (unix_peer(sk) == other) { + if (sk->sk_type == SOCK_SEQPACKET) { + /* We are here only when racing with unix_release_sock() + * is clearing @other. Never change state to TCP_CLOSE + * unlike SOCK_DGRAM wants. + */ + unix_state_unlock(sk); + err = -EPIPE; + } else if (unix_peer(sk) == other) { unix_peer(sk) = NULL; unix_dgram_peer_wake_disconnect_wakeup(sk, other); + sk->sk_state = TCP_CLOSE; unix_state_unlock(sk); - sk->sk_state = TCP_CLOSE; unix_dgram_disconnected(sk, other); sock_put(other); err = -ECONNREFUSED; -- 2.35.1