From: Guillaume Nault Date: Mon, 3 Apr 2017 10:03:13 +0000 (+0200) Subject: l2tp: take reference on sessions being dumped X-Git-Tag: v3.2.91~28 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=2b846c841db527fe9afff23b70c265b1809cd792 l2tp: take reference on sessions being dumped 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 3.2: adjust context] Signed-off-by: Ben Hutchings --- diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index 8ce9cb489df1..3954b18f42ee 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -275,7 +275,8 @@ struct l2tp_session *l2tp_session_get(struct net *net, } 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 hlist_node *walk; @@ -286,6 +287,9 @@ struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth) for (hash = 0; hash < L2TP_HASH_SIZE; hash++) { hlist_for_each_entry(session, walk, &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; } @@ -296,7 +300,7 @@ struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth) 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. diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h index 522d6aa2a4a6..1caf21e11822 100644 --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -226,7 +226,8 @@ struct l2tp_session *l2tp_session_get(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id, bool do_ref); extern struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id); -extern 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); extern struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id); diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c index 76130134bfa6..8bb0d56c822b 100644 --- a/net/l2tp/l2tp_debugfs.c +++ b/net/l2tp/l2tp_debugfs.c @@ -51,7 +51,7 @@ static void l2tp_dfs_next_tunnel(struct l2tp_dfs_seq_data *pd) 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) { @@ -227,10 +227,14 @@ static int l2tp_dfs_seq_show(struct seq_file *m, void *v) } /* 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; diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c index 2b8048f452fe..6fd632285106 100644 --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -669,7 +669,7 @@ static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback goto out; } - session = l2tp_session_find_nth(tunnel, si); + session = l2tp_session_get_nth(tunnel, si, false); if (session == NULL) { ti++; tunnel = NULL; @@ -679,8 +679,11 @@ static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback if (l2tp_nl_session_send(skb, NETLINK_CB(cb->skb).pid, cb->nlh->nlmsg_seq, NLM_F_MULTI, - session) <= 0) + session) <= 0) { + l2tp_session_dec_refcount(session); break; + } + l2tp_session_dec_refcount(session); si++; } diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c index dae5a6d9e160..c404a6a8dd74 100644 --- a/net/l2tp/l2tp_ppp.c +++ b/net/l2tp/l2tp_ppp.c @@ -1564,7 +1564,7 @@ static void pppol2tp_next_tunnel(struct net *net, struct pppol2tp_seq_data *pd) 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) { @@ -1691,10 +1691,14 @@ static int pppol2tp_seq_show(struct seq_file *m, void *v) /* 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;