From 2d45a02d0166caf2627fe91897c6ffc3b19514c4 Mon Sep 17 00:00:00 2001 From: Marcelo Ricardo Leitner Date: Fri, 12 Jun 2015 10:16:41 -0300 Subject: [PATCH] sctp: fix ASCONF list handling ->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 using ->addr_wq_lock spinlock to protect the list. A special handling is done upon socket creation and destruction for that. Error handlig on sctp_init_sock() will never return an error after having initialized asconf, so sctp_destroy_sock() can be called without addrq_wq_lock. The lock now will be take on sctp_close_sock(), before locking the socket, so we don't do it in inverse order compared to sctp_addr_wq_timeout_handler(). 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 Suggested-by: Neil Horman Suggested-by: Hannes Frederic Sowa Acked-by: Hannes Frederic Sowa Signed-off-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller --- include/net/netns/sctp.h | 1 + include/net/sctp/structs.h | 4 ++++ net/sctp/socket.c | 43 ++++++++++++++++++++++++++++---------- 3 files changed, 37 insertions(+), 11 deletions(-) diff --git a/include/net/netns/sctp.h b/include/net/netns/sctp.h index 3573a81815ad..8ba379f9e467 100644 --- a/include/net/netns/sctp.h +++ b/include/net/netns/sctp.h @@ -31,6 +31,7 @@ struct netns_sctp { struct list_head addr_waitq; struct timer_list addr_wq_timer; struct list_head 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 2bb2fcf5b11f..495c87e367b3 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/socket.c b/net/sctp/socket.c index f09de7fac2e6..5f6c4e61325b 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -1528,8 +1528,10 @@ static void sctp_close(struct sock *sk, long timeout) /* Supposedly, no process has access to the socket, but * the net layers still may. + * Also, sctp_destroy_sock() needs to be called with addr_wq_lock + * held and that should be grabbed before socket lock. */ - local_bh_disable(); + spin_lock_bh(&net->sctp.addr_wq_lock); bh_lock_sock(sk); /* Hold the sock, since sk_common_release() will put sock_put() @@ -1539,7 +1541,7 @@ static void sctp_close(struct sock *sk, long timeout) sk_common_release(sk); bh_unlock_sock(sk); - local_bh_enable(); + spin_unlock_bh(&net->sctp.addr_wq_lock); sock_put(sk); @@ -3580,6 +3582,7 @@ 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; @@ -3588,6 +3591,7 @@ static int sctp_setsockopt_auto_asconf(struct sock *sk, char __user *optval, &sock_net(sk)->sctp.auto_asconf_splist); sp->do_auto_asconf = 1; } + spin_unlock_bh(&sock_net(sk)->sctp.addr_wq_lock); return 0; } @@ -4121,18 +4125,28 @@ static int sctp_init_sock(struct sock *sk) local_bh_disable(); percpu_counter_inc(&sctp_sockets_allocated); sock_prot_inuse_add(net, sk->sk_prot, 1); + + /* Nothing can fail after this block, otherwise + * sctp_destroy_sock() will be called without addr_wq_lock held + */ if (net->sctp.default_auto_asconf) { + spin_lock(&sock_net(sk)->sctp.addr_wq_lock); list_add_tail(&sp->auto_asconf_list, &net->sctp.auto_asconf_splist); sp->do_auto_asconf = 1; - } else + spin_unlock(&sock_net(sk)->sctp.addr_wq_lock); + } else { sp->do_auto_asconf = 0; + } + local_bh_enable(); return 0; } -/* Cleanup any SCTP per socket resources. */ +/* Cleanup any SCTP per socket resources. Must be called with + * sock_net(sk)->sctp.addr_wq_lock held if sp->do_auto_asconf is true + */ static void sctp_destroy_sock(struct sock *sk) { struct sctp_sock *sp; @@ -7195,6 +7209,19 @@ 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 +7236,6 @@ 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 +7243,7 @@ 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. -- 2.20.1