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 5CA741C31 for ; Wed, 23 Nov 2022 09:51:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99A5EC433D6; Wed, 23 Nov 2022 09:51:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669197102; bh=4jyIn4YoUOj/Xcn3qfyKUaQfbIVvRlVpgVTshiyEAv4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QZF5Sw4EjWmqN0BgdXnQomLuBBcZKJRKgS5vczPQpbfKH06Z81e+XyJCtOyMyFuqC PhERpQNAT6vWdQWNh/Hs2XRMCrWJeyJ1TNZLQwvKotuSSvFwzOrvzjB5R5bUezENgH 1g213Of1C4x84mV6Ylcq5J6jVaNYCd8GAE0pWzWA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+278279efdd2730dd14bf@syzkaller.appspotmail.com, shaozhengchao , Paolo Abeni , Tom Herbert , Cong Wang , Sasha Levin Subject: [PATCH 6.0 171/314] kcm: close race conditions on sk_receive_queue Date: Wed, 23 Nov 2022 09:50:16 +0100 Message-Id: <20221123084633.316460482@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084625.457073469@linuxfoundation.org> References: <20221123084625.457073469@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: Cong Wang [ Upstream commit 5121197ecc5db58c07da95eb1ff82b98b121a221 ] sk->sk_receive_queue is protected by skb queue lock, but for KCM sockets its RX path takes mux->rx_lock to protect more than just skb queue. However, kcm_recvmsg() still only grabs the skb queue lock, so race conditions still exist. We can teach kcm_recvmsg() to grab mux->rx_lock too but this would introduce a potential performance regression as struct kcm_mux can be shared by multiple KCM sockets. So we have to enforce skb queue lock in requeue_rx_msgs() and handle skb peek case carefully in kcm_wait_data(). Fortunately, skb_recv_datagram() already handles it nicely and is widely used by other sockets, we can just switch to skb_recv_datagram() after getting rid of the unnecessary sock lock in kcm_recvmsg() and kcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets, so it is safe to get rid of this check too. I ran the original syzbot reproducer for 30 min without seeing any issue. Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Reported-by: syzbot+278279efdd2730dd14bf@syzkaller.appspotmail.com Reported-by: shaozhengchao Cc: Paolo Abeni Cc: Tom Herbert Signed-off-by: Cong Wang Link: https://lore.kernel.org/r/20221114005119.597905-1-xiyou.wangcong@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/kcm/kcmsock.c | 58 +++++------------------------------------------ 1 file changed, 6 insertions(+), 52 deletions(-) diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c index befc62606cdf..9e4b40a30a72 100644 --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -222,7 +222,7 @@ static void requeue_rx_msgs(struct kcm_mux *mux, struct sk_buff_head *head) struct sk_buff *skb; struct kcm_sock *kcm; - while ((skb = __skb_dequeue(head))) { + while ((skb = skb_dequeue(head))) { /* Reset destructor to avoid calling kcm_rcv_ready */ skb->destructor = sock_rfree; skb_orphan(skb); @@ -1085,53 +1085,17 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) return err; } -static struct sk_buff *kcm_wait_data(struct sock *sk, int flags, - long timeo, int *err) -{ - struct sk_buff *skb; - - while (!(skb = skb_peek(&sk->sk_receive_queue))) { - if (sk->sk_err) { - *err = sock_error(sk); - return NULL; - } - - if (sock_flag(sk, SOCK_DONE)) - return NULL; - - if ((flags & MSG_DONTWAIT) || !timeo) { - *err = -EAGAIN; - return NULL; - } - - sk_wait_data(sk, &timeo, NULL); - - /* Handle signals */ - if (signal_pending(current)) { - *err = sock_intr_errno(timeo); - return NULL; - } - } - - return skb; -} - static int kcm_recvmsg(struct socket *sock, struct msghdr *msg, size_t len, int flags) { struct sock *sk = sock->sk; struct kcm_sock *kcm = kcm_sk(sk); int err = 0; - long timeo; struct strp_msg *stm; int copied = 0; struct sk_buff *skb; - timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); - - lock_sock(sk); - - skb = kcm_wait_data(sk, flags, timeo, &err); + skb = skb_recv_datagram(sk, flags, &err); if (!skb) goto out; @@ -1162,14 +1126,11 @@ static int kcm_recvmsg(struct socket *sock, struct msghdr *msg, /* Finished with message */ msg->msg_flags |= MSG_EOR; KCM_STATS_INCR(kcm->stats.rx_msgs); - skb_unlink(skb, &sk->sk_receive_queue); - kfree_skb(skb); } } out: - release_sock(sk); - + skb_free_datagram(sk, skb); return copied ? : err; } @@ -1179,7 +1140,6 @@ static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos, { struct sock *sk = sock->sk; struct kcm_sock *kcm = kcm_sk(sk); - long timeo; struct strp_msg *stm; int err = 0; ssize_t copied; @@ -1187,11 +1147,7 @@ static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos, /* Only support splice for SOCKSEQPACKET */ - timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); - - lock_sock(sk); - - skb = kcm_wait_data(sk, flags, timeo, &err); + skb = skb_recv_datagram(sk, flags, &err); if (!skb) goto err_out; @@ -1219,13 +1175,11 @@ static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos, * finish reading the message. */ - release_sock(sk); - + skb_free_datagram(sk, skb); return copied; err_out: - release_sock(sk); - + skb_free_datagram(sk, skb); return err; } -- 2.35.1