Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752560AbdGPOfO (ORCPT ); Sun, 16 Jul 2017 10:35:14 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:44258 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752913AbdGPOOb (ORCPT ); Sun, 16 Jul 2017 10:14:31 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David S. Miller" , "Guillaume Nault" Date: Sun, 16 Jul 2017 14:56:46 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 123/178] l2tp: take reference on sessions being dumped In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5295 Lines: 158 3.16.46-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Guillaume Nault commit e08293a4ccbcc993ded0fdc46f1e57926b833d63 upstream. Take a reference on the sessions returned by l2tp_session_find_nth() (and rename it l2tp_session_get_nth() to reflect this change), so that caller is assured that the session isn't going to disappear while processing it. For procfs and debugfs handlers, the session is held in the .start() callback and dropped in .show(). Given that pppol2tp_seq_session_show() dereferences the associated PPPoL2TP socket and that l2tp_dfs_seq_session_show() might call pppol2tp_show(), we also need to call the session's .ref() callback to prevent the socket from going away from under us. Fixes: fd558d186df2 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts") Fixes: 0ad6614048cf ("l2tp: Add debugfs files for dumping l2tp debug info") Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP") Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- net/l2tp/l2tp_core.c | 8 ++++++-- net/l2tp/l2tp_core.h | 3 ++- net/l2tp/l2tp_debugfs.c | 10 +++++++--- net/l2tp/l2tp_netlink.c | 7 +++++-- net/l2tp/l2tp_ppp.c | 10 +++++++--- 5 files changed, 27 insertions(+), 11 deletions(-) --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -326,7 +326,8 @@ struct l2tp_session *l2tp_session_get(st } EXPORT_SYMBOL_GPL(l2tp_session_get); -struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth) +struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth, + bool do_ref) { int hash; struct l2tp_session *session; @@ -336,6 +337,9 @@ struct l2tp_session *l2tp_session_find_n for (hash = 0; hash < L2TP_HASH_SIZE; hash++) { hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) { if (++count > nth) { + l2tp_session_inc_refcount(session); + if (do_ref && session->ref) + session->ref(session); read_unlock_bh(&tunnel->hlist_lock); return session; } @@ -346,7 +350,7 @@ struct l2tp_session *l2tp_session_find_n return NULL; } -EXPORT_SYMBOL_GPL(l2tp_session_find_nth); +EXPORT_SYMBOL_GPL(l2tp_session_get_nth); /* Lookup a session by interface name. * This is very inefficient but is only used by management interfaces. --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -246,7 +246,8 @@ struct l2tp_session *l2tp_session_get(st struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id); -struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth); +struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth, + bool do_ref); struct l2tp_session *l2tp_session_get_by_ifname(struct net *net, char *ifname, bool do_ref); struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id); --- a/net/l2tp/l2tp_debugfs.c +++ b/net/l2tp/l2tp_debugfs.c @@ -53,7 +53,7 @@ static void l2tp_dfs_next_tunnel(struct static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd) { - pd->session = l2tp_session_find_nth(pd->tunnel, pd->session_idx); + pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx, true); pd->session_idx++; if (pd->session == NULL) { @@ -238,10 +238,14 @@ static int l2tp_dfs_seq_show(struct seq_ } /* Show the tunnel or session context */ - if (pd->session == NULL) + if (!pd->session) { l2tp_dfs_seq_tunnel_show(m, pd->tunnel); - else + } else { l2tp_dfs_seq_session_show(m, pd->session); + if (pd->session->deref) + pd->session->deref(pd->session); + l2tp_session_dec_refcount(pd->session); + } out: return 0; --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -740,7 +740,7 @@ static int l2tp_nl_cmd_session_dump(stru goto out; } - session = l2tp_session_find_nth(tunnel, si); + session = l2tp_session_get_nth(tunnel, si, false); if (session == NULL) { ti++; tunnel = NULL; @@ -750,8 +750,11 @@ static int l2tp_nl_cmd_session_dump(stru if (l2tp_nl_session_send(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq, NLM_F_MULTI, - session) <= 0) + session) <= 0) { + l2tp_session_dec_refcount(session); break; + } + l2tp_session_dec_refcount(session); si++; } --- a/net/l2tp/l2tp_ppp.c +++ b/net/l2tp/l2tp_ppp.c @@ -1579,7 +1579,7 @@ static void pppol2tp_next_tunnel(struct static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd) { - pd->session = l2tp_session_find_nth(pd->tunnel, pd->session_idx); + pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx, true); pd->session_idx++; if (pd->session == NULL) { @@ -1706,10 +1706,14 @@ static int pppol2tp_seq_show(struct seq_ /* Show the tunnel or session context. */ - if (pd->session == NULL) + if (!pd->session) { pppol2tp_seq_tunnel_show(m, pd->tunnel); - else + } else { pppol2tp_seq_session_show(m, pd->session); + if (pd->session->deref) + pd->session->deref(pd->session); + l2tp_session_dec_refcount(pd->session); + } out: return 0;