Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753084AbbLLUSh (ORCPT ); Sat, 12 Dec 2015 15:18:37 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:37295 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753808AbbLLUQw (ORCPT ); Sat, 12 Dec 2015 15:16:52 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro , Eric Dumazet , Hannes Frederic Sowa , "David S. Miller" Subject: [PATCH 4.3 07/71] af-unix: passcred support for sendpage Date: Sat, 12 Dec 2015 12:05:31 -0800 Message-Id: <20151212200537.117668385@linuxfoundation.org> X-Mailer: git-send-email 2.6.4 In-Reply-To: <20151212200536.761001328@linuxfoundation.org> References: <20151212200536.761001328@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5679 Lines: 201 4.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hannes Frederic Sowa [ Upstream commit 9490f886b192964796285907d777ff00fba1fa0f ] sendpage did not care about credentials at all. This could lead to situations in which because of fd passing between processes we could append data to skbs with different scm data. It is illegal to splice those skbs together. Instead we have to allocate a new skb and if requested fill out the scm details. Fixes: 869e7c62486ec ("net: af_unix: implement stream sendpage support") Reported-by: Al Viro Cc: Al Viro Cc: Eric Dumazet Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/unix/af_unix.c | 79 ++++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 64 insertions(+), 15 deletions(-) --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1550,6 +1550,14 @@ static int unix_scm_to_skb(struct scm_co return err; } +static bool unix_passcred_enabled(const struct socket *sock, + const struct sock *other) +{ + return test_bit(SOCK_PASSCRED, &sock->flags) || + !other->sk_socket || + test_bit(SOCK_PASSCRED, &other->sk_socket->flags); +} + /* * Some apps rely on write() giving SCM_CREDENTIALS * We include credentials if source or destination socket @@ -1560,14 +1568,41 @@ static void maybe_add_creds(struct sk_bu { if (UNIXCB(skb).pid) return; - if (test_bit(SOCK_PASSCRED, &sock->flags) || - !other->sk_socket || - test_bit(SOCK_PASSCRED, &other->sk_socket->flags)) { + if (unix_passcred_enabled(sock, other)) { UNIXCB(skb).pid = get_pid(task_tgid(current)); current_uid_gid(&UNIXCB(skb).uid, &UNIXCB(skb).gid); } } +static int maybe_init_creds(struct scm_cookie *scm, + struct socket *socket, + const struct sock *other) +{ + int err; + struct msghdr msg = { .msg_controllen = 0 }; + + err = scm_send(socket, &msg, scm, false); + if (err) + return err; + + if (unix_passcred_enabled(socket, other)) { + scm->pid = get_pid(task_tgid(current)); + current_uid_gid(&scm->creds.uid, &scm->creds.gid); + } + return err; +} + +static bool unix_skb_scm_eq(struct sk_buff *skb, + struct scm_cookie *scm) +{ + const struct unix_skb_parms *u = &UNIXCB(skb); + + return u->pid == scm->pid && + uid_eq(u->uid, scm->creds.uid) && + gid_eq(u->gid, scm->creds.gid) && + unix_secdata_eq(scm, skb); +} + /* * Send AF_UNIX data. */ @@ -1883,8 +1918,10 @@ out_err: static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page, int offset, size_t size, int flags) { - int err = 0; - bool send_sigpipe = true; + int err; + bool send_sigpipe = false; + bool init_scm = true; + struct scm_cookie scm; struct sock *other, *sk = socket->sk; struct sk_buff *skb, *newskb = NULL, *tail = NULL; @@ -1902,7 +1939,7 @@ alloc_skb: newskb = sock_alloc_send_pskb(sk, 0, 0, flags & MSG_DONTWAIT, &err, 0); if (!newskb) - return err; + goto err; } /* we must acquire readlock as we modify already present @@ -1911,12 +1948,12 @@ alloc_skb: err = mutex_lock_interruptible(&unix_sk(other)->readlock); if (err) { err = flags & MSG_DONTWAIT ? -EAGAIN : -ERESTARTSYS; - send_sigpipe = false; goto err; } if (sk->sk_shutdown & SEND_SHUTDOWN) { err = -EPIPE; + send_sigpipe = true; goto err_unlock; } @@ -1925,17 +1962,27 @@ alloc_skb: if (sock_flag(other, SOCK_DEAD) || other->sk_shutdown & RCV_SHUTDOWN) { err = -EPIPE; + send_sigpipe = true; goto err_state_unlock; } + if (init_scm) { + err = maybe_init_creds(&scm, socket, other); + if (err) + goto err_state_unlock; + init_scm = false; + } + skb = skb_peek_tail(&other->sk_receive_queue); if (tail && tail == skb) { skb = newskb; - } else if (!skb) { - if (newskb) + } else if (!skb || !unix_skb_scm_eq(skb, &scm)) { + if (newskb) { skb = newskb; - else + } else { + tail = skb; goto alloc_skb; + } } else if (newskb) { /* this is fast path, we don't necessarily need to * call to kfree_skb even though with newskb == NULL @@ -1956,6 +2003,9 @@ alloc_skb: atomic_add(size, &sk->sk_wmem_alloc); if (newskb) { + err = unix_scm_to_skb(&scm, skb, false); + if (err) + goto err_state_unlock; spin_lock(&other->sk_receive_queue.lock); __skb_queue_tail(&other->sk_receive_queue, newskb); spin_unlock(&other->sk_receive_queue.lock); @@ -1965,7 +2015,7 @@ alloc_skb: mutex_unlock(&unix_sk(other)->readlock); other->sk_data_ready(other); - + scm_destroy(&scm); return size; err_state_unlock: @@ -1976,6 +2026,8 @@ err: kfree_skb(newskb); if (send_sigpipe && !(flags & MSG_NOSIGNAL)) send_sig(SIGPIPE, current, 0); + if (!init_scm) + scm_destroy(&scm); return err; } @@ -2279,10 +2331,7 @@ unlock: if (check_creds) { /* Never glue messages from different writers */ - if ((UNIXCB(skb).pid != scm.pid) || - !uid_eq(UNIXCB(skb).uid, scm.creds.uid) || - !gid_eq(UNIXCB(skb).gid, scm.creds.gid) || - !unix_secdata_eq(&scm, skb)) + if (!unix_skb_scm_eq(skb, &scm)) break; } else if (test_bit(SOCK_PASSCRED, &sock->flags)) { /* Copy credentials */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/