[Devel] [PATCH] ve: Kill tcp_v4_kill_ve_sockets()
Kirill Tkhai
ktkhai at odin.com
Mon Jun 1 05:46:30 PDT 2015
В Пн, 01/06/2015 в 15:16 +0300, Vasily Averin пишет:
> On 01.06.2015 14:31, Kirill Tkhai wrote:
> > В Пт, 29/05/2015 в 17:20 +0300, Andrew Vagin пишет:
> >> Acked-by: Andrew Vagin <avagin at odin.com>
> >>
> >> I'm agree that we need to remove this function, but I don't know how it
> >> fixes the bug.
> >
> > tcp_v4_kill_ve_sockets() is called when all processes are killed,
> > and their sockets have been already replaced with time wait sockets.
> >
> > So, when we are iterating through chain list:
> >
> > sk_nulls_for_each(sk, node, &head[i].chain)
> >
> > we can't find TCP sockets there. Every sk is of type inet_timewait_sock.
> > Yes, they both are linked in the same table.
> >
> > struct sock (tcp_sock) and inet_timewait_sock are not a child and a parent:
> >
> > struct sock { struct inet_timewait_sock {
> > struct sock_common __sk_common; struct sock_common __tw_common;
> > socket_lock_t sk_lock; int tw_timeout;
> >
> > They are different.
> >
> > So, when we are doing bh_lock_sock(sk) in tcp_v4_kill_ve_sockets(), i.e.
> >
> > #define bh_lock_sock(__sk) spin_lock(&((__sk)->sk_lock.slock))
> >
> > we are trying to manipulate with tw_timeout, which is not zero, and can't
> > acquire the spinlock.
>
> it's nice theory, but I still do not understand how is it related to observed crash?
>
> I did not found such process in crash dump of PSBM-33755.
> Kernel was crashed in another function, not on access to spinlock.
> and it was happen in 50 seconds after stop of CT 106.
> How can you explain it?
You dereference time wait socket in tcp_v4_kill_ve_sockets() and use it
as tcp socket. Starting from bh_lock_sock() and further in tcp_kill_ve_onesk()
you're modifying a memory of tw socket like it'd be a tcp_sk, and this
leads to memory corruption.
Another one problem is you can't install a time wait socket for a time wait
socket. When you do that, you're replacing old tw sock with a new in hashtable,
but it still remains to be linked in death row using tw_death_node.
> >> On Fri, May 29, 2015 at 04:53:39PM +0300, Kirill Tkhai wrote:
> >>> This is a leftover from earlier versions of PCS,
> >>> and we do not need that functionality in 3.10.
> >>>
> >>> It was the reason of the kernel panic in 2.6.32:
> >>> https://jira.sw.ru/browse/PSBM-33755, in the test
> >>> of forced CT destroying.
> >>>
> >>> Also, tcp_v4_kill_ve_sockets() looks as the only
> >>> user of synchronize_net(), so we're not need this
> >>> function too (the only net hook fini_venet_acct_ip6_stat()
> >>> from the chain doesn't need it). Besides this, there
> >>> will be one more synchronize_rcu() later in
> >>> ve_drop_context().
> >>>
> >>> Signed-off-by: Kirill Tkhai <ktkhai at odin.com>
> >>> ---
> >>> include/linux/ve_proto.h | 5 +--
> >>> kernel/ve/ve.c | 5 +--
> >>> net/ipv4/tcp_ipv4.c | 88 ----------------------------------------------
> >>> 3 files changed, 2 insertions(+), 96 deletions(-)
> >>>
> >>> diff --git a/include/linux/ve_proto.h b/include/linux/ve_proto.h
> >>> index d491ab0..e77d6f9 100644
> >>> --- a/include/linux/ve_proto.h
> >>> +++ b/include/linux/ve_proto.h
> >>> @@ -50,12 +50,9 @@ typedef void (*ve_seq_print_t)(struct seq_file *, struct ve_struct *);
> >>> void vzmon_register_veaddr_print_cb(ve_seq_print_t);
> >>> void vzmon_unregister_veaddr_print_cb(ve_seq_print_t);
> >>>
> >>> -#ifdef CONFIG_INET
> >>> -void tcp_v4_kill_ve_sockets(struct ve_struct *envid);
> >>> -#ifdef CONFIG_VE_NETDEV
> >>> +#if defined(CONFIG_INET) && defined(CONFIG_VE_NETDEV)
> >>> int venet_init(void);
> >>> #endif
> >>> -#endif
> >>>
> >>> extern struct list_head ve_list_head;
> >>> #define for_each_ve(ve) list_for_each_entry((ve), &ve_list_head, ve_list)
> >>> diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
> >>> index 55b7d86..3128fdb 100644
> >>> --- a/kernel/ve/ve.c
> >>> +++ b/kernel/ve/ve.c
> >>> @@ -647,10 +647,7 @@ void ve_exit_ns(struct pid_namespace *pid_ns)
> >>>
> >>> down_write(&ve->op_sem);
> >>> ve_hook_iterate_fini(VE_SS_CHAIN, ve);
> >>> -#ifdef CONFIG_INET
> >>> - tcp_v4_kill_ve_sockets(ve);
> >>> - synchronize_net();
> >>> -#endif
> >>> +
> >>> ve_list_del(ve);
> >>> ve_drop_context(ve);
> >>> up_write(&ve->op_sem);
> >>> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> >>> index ad4520c..a8ef57a 100644
> >>> --- a/net/ipv4/tcp_ipv4.c
> >>> +++ b/net/ipv4/tcp_ipv4.c
> >>> @@ -2812,91 +2812,3 @@ void __init tcp_v4_init(void)
> >>> if (register_pernet_subsys(&tcp_sk_ops))
> >>> panic("Failed to create the TCP control socket.\n");
> >>> }
> >>> -
> >>> -#ifdef CONFIG_VE
> >>> -static void tcp_kill_ve_onesk(struct sock *sk)
> >>> -{
> >>> - struct tcp_sock *tp = tcp_sk(sk);
> >>> -
> >>> - /* Check the assumed state of the socket. */
> >>> - if (!sock_flag(sk, SOCK_DEAD)) {
> >>> - printk(KERN_WARNING "Killing sk: dead %d, state %d, "
> >>> - "wrseq %u unseq %u, wrqu %d.\n",
> >>> - sock_flag(sk, SOCK_DEAD), sk->sk_state,
> >>> - tp->write_seq, tp->snd_una,
> >>> - !skb_queue_empty(&sk->sk_write_queue));
> >>> - sk->sk_err = ECONNRESET;
> >>> - sk->sk_error_report(sk);
> >>> - }
> >>> -
> >>> - tcp_send_active_reset(sk, GFP_ATOMIC);
> >>> - switch (sk->sk_state) {
> >>> - case TCP_FIN_WAIT1:
> >>> - case TCP_CLOSING:
> >>> - /* In these 2 states the peer may want us to retransmit
> >>> - * some data and/or FIN. Entering "resetting mode"
> >>> - * instead.
> >>> - */
> >>> - tcp_time_wait(sk, TCP_CLOSE, 0);
> >>> - break;
> >>> - case TCP_FIN_WAIT2:
> >>> - /* By some reason the socket may stay in this state
> >>> - * without turning into a TW bucket. Fix it.
> >>> - */
> >>> - tcp_time_wait(sk, TCP_FIN_WAIT2, 0);
> >>> - break;
> >>> - default:
> >>> - /* Just jump into CLOSED state. */
> >>> - tcp_done(sk);
> >>> - break;
> >>> - }
> >>> -}
> >>> -
> >>> -void tcp_v4_kill_ve_sockets(struct ve_struct *envid)
> >>> -{
> >>> - struct inet_ehash_bucket *head;
> >>> - int i, retry;
> >>> -
> >>> - /* alive */
> >>> -again:
> >>> - retry = 0;
> >>> - local_bh_disable();
> >>> - head = tcp_hashinfo.ehash;
> >>> - for (i = 0; i < tcp_hashinfo.ehash_mask; i++) {
> >>> - struct sock *sk;
> >>> - struct hlist_nulls_node *node;
> >>> - spinlock_t *lock = inet_ehash_lockp(&tcp_hashinfo, i);
> >>> -more_work:
> >>> - spin_lock(lock);
> >>> - sk_nulls_for_each(sk, node, &head[i].chain) {
> >>> - if (sock_net(sk)->owner_ve == envid) {
> >>> - sock_hold(sk);
> >>> - spin_unlock(lock);
> >>> -
> >>> - bh_lock_sock(sk);
> >>> - if (sock_owned_by_user(sk)) {
> >>> - retry = 1;
> >>> - bh_unlock_sock(sk);
> >>> - sock_put(sk);
> >>> - goto enable_bh;
> >>> - }
> >>> - /* sk might have disappeared from the hash before
> >>> - * we got the lock */
> >>> - if (sk->sk_state != TCP_CLOSE)
> >>> - tcp_kill_ve_onesk(sk);
> >>> - bh_unlock_sock(sk);
> >>> - sock_put(sk);
> >>> - goto more_work;
> >>> - }
> >>> - }
> >>> - spin_unlock(lock);
> >>> - }
> >>> -enable_bh:
> >>> - local_bh_enable();
> >>> - if (retry) {
> >>> - schedule_timeout_interruptible(HZ);
> >>> - goto again;
> >>> - }
> >>> -}
> >>> -EXPORT_SYMBOL(tcp_v4_kill_ve_sockets);
> >>> -#endif
> >>>
> >
> >
> > _______________________________________________
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> >
> >
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