[PATCH v2 2/2] sctp: fix ASCONF list handling
From: <hidden>
Date: 2015-06-03 16:54:31
Also in:
linux-sctp
Subsystem:
networking [general], sctp protocol, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Marcelo Ricardo Leitner, Xin Long, Linus Torvalds
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
->auto_asconf_splist is per namespace and mangled by functions like
sctp_setsockopt_auto_asconf() which doesn't guarantee any serialization.
Also, the call to inet_sk_copy_descendant() was backuping
->auto_asconf_list through the copy but was not honoring
->do_auto_asconf, which could lead to list corruption if it was
different between both sockets.
This commit thus fixes the list handling by rcu-ifying it and using
->addr_wq_lock spinlock to protect against multiple writers.
Instead of taking the lock on sctp_sock_migrate() for copying and
restoring the list values, it's preferred to avoid rewritting it by
implementing sctp_copy_descendant().
Issue was found with a test application that kept flipping sysctl
default_auto_asconf on and off, but one could trigger it by issuing
simultaneous setsockopt() calls on multiple sockets or by
creating/destroying sockets fast enough. This is only triggerable
locally.
Fixes: 9f7d653b67ae ("sctp: Add Auto-ASCONF support (core).")
Reported-by: Ji Jianwen <redacted>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
---
include/net/netns/sctp.h | 3 ++-
include/net/sctp/structs.h | 4 ++++
net/sctp/protocol.c | 3 ++-
net/sctp/socket.c | 39 ++++++++++++++++++++++++++-------------
4 files changed, 34 insertions(+), 15 deletions(-)
diff --git a/include/net/netns/sctp.h b/include/net/netns/sctp.h
index 9e53412c4ed829e8e45777a6d95406d490dbaa75..161de47076ebee2ffce2b777a61e673e576fd982 100644
--- a/include/net/netns/sctp.h
+++ b/include/net/netns/sctp.h@@ -30,7 +30,8 @@ struct netns_sctp { struct list_head local_addr_list; struct list_head __rcu addr_waitq; struct timer_list addr_wq_timer; - struct list_head auto_asconf_splist; + struct list_head __rcu auto_asconf_splist; + /* Lock that protects both addr_waitq and auto_asconf_splist */ spinlock_t addr_wq_lock; /* Lock that protects the local_addr_list writers */
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 2bb2fcf5b11f0387c81b860ad2d3a6607da19a7d..495c87e367b3f2e8941807f56a77d2e14469bfed 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h@@ -223,6 +223,10 @@ struct sctp_sock { atomic_t pd_mode; /* Receive to here while partial delivery is in effect. */ struct sk_buff_head pd_lobby; + + /* These must be the last fields, as they will skipped on copies, + * like on accept and peeloff operations + */ struct list_head auto_asconf_list; int do_auto_asconf; };
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index a5089883b28195f3aef69ef35b5397322a01126f..e4b24ef9340da210de0b0076f8a42080e991527e 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c@@ -665,7 +665,8 @@ static void sctp_addr_wq_timeout_handler(unsigned long arg) } } #endif - list_for_each_entry(sp, &net->sctp.auto_asconf_splist, auto_asconf_list) { + list_for_each_entry_rcu(sp, &net->sctp.auto_asconf_splist, + auto_asconf_list) { struct sock *sk; sk = sctp_opt2sk(sp);
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index f09de7fac2e6acddad8b2e046dbf626e329cb674..475f84f80e5448f1f33d213dd9c3eae08365610f 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c@@ -3580,14 +3580,16 @@ static int sctp_setsockopt_auto_asconf(struct sock *sk, char __user *optval, if ((val && sp->do_auto_asconf) || (!val && !sp->do_auto_asconf)) return 0; + spin_lock_bh(&sock_net(sk)->sctp.addr_wq_lock); if (val == 0 && sp->do_auto_asconf) { - list_del(&sp->auto_asconf_list); sp->do_auto_asconf = 0; + list_del_rcu(&sp->auto_asconf_list); } else if (val && !sp->do_auto_asconf) { - list_add_tail(&sp->auto_asconf_list, - &sock_net(sk)->sctp.auto_asconf_splist); sp->do_auto_asconf = 1; + list_add_tail_rcu(&sp->auto_asconf_list, + &sock_net(sk)->sctp.auto_asconf_splist); } + spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock); return 0; }
@@ -4122,9 +4124,11 @@ static int sctp_init_sock(struct sock *sk) percpu_counter_inc(&sctp_sockets_allocated); sock_prot_inuse_add(net, sk->sk_prot, 1); if (net->sctp.default_auto_asconf) { - list_add_tail(&sp->auto_asconf_list, - &net->sctp.auto_asconf_splist); + spin_lock_bh(&sock_net(sk)->sctp.addr_wq_lock); sp->do_auto_asconf = 1; + list_add_tail_rcu(&sp->auto_asconf_list, + &net->sctp.auto_asconf_splist); + spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock); } else sp->do_auto_asconf = 0; local_bh_enable();
@@ -4148,8 +4152,10 @@ static void sctp_destroy_sock(struct sock *sk) return; if (sp->do_auto_asconf) { + spin_lock_bh(&sock_net(sk)->sctp.addr_wq_lock); sp->do_auto_asconf = 0; - list_del(&sp->auto_asconf_list); + list_del_rcu(&sp->auto_asconf_list); + spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock); } sctp_endpoint_free(sp->ep); local_bh_disable();
@@ -7195,6 +7201,19 @@ void sctp_copy_sock(struct sock *newsk, struct sock *sk, newinet->mc_list = NULL; } +static inline void sctp_copy_descendant(struct sock *sk_to, + const struct sock *sk_from) +{ + int ancestor_size = sizeof(struct inet_sock) + + sizeof(struct sctp_sock) - + offsetof(struct sctp_sock, auto_asconf_list); + + if (sk_from->sk_family == PF_INET6) + ancestor_size += sizeof(struct ipv6_pinfo); + + __inet_sk_copy_descendant(sk_to, sk_from, ancestor_size); +} + /* Populate the fields of the newsk from the oldsk and migrate the assoc * and its messages to the newsk. */
@@ -7209,7 +7228,6 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk, struct sk_buff *skb, *tmp; struct sctp_ulpevent *event; struct sctp_bind_hashbucket *head; - struct list_head tmplist; /* Migrate socket buffer sizes and all the socket level options to the * new socket.
@@ -7217,12 +7235,7 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk, newsk->sk_sndbuf = oldsk->sk_sndbuf; newsk->sk_rcvbuf = oldsk->sk_rcvbuf; /* Brute force copy old sctp opt. */ - if (oldsp->do_auto_asconf) { - memcpy(&tmplist, &newsp->auto_asconf_list, sizeof(tmplist)); - inet_sk_copy_descendant(newsk, oldsk); - memcpy(&newsp->auto_asconf_list, &tmplist, sizeof(tmplist)); - } else - inet_sk_copy_descendant(newsk, oldsk); + sctp_copy_descendant(newsk, oldsk); /* Restore the ep value that was overwritten with the above structure * copy.
--
2.4.1