From d315492b1a6ba29da0fa2860759505ae1b2db857 Mon Sep 17 00:00:00 2001 From: Daniel Lezcano Date: Mon, 8 Sep 2008 13:17:27 -0700 Subject: [PATCH] netns : fix kernel panic in timewait socket destruction How to reproduce ? - create a network namespace - use tcp protocol and get timewait socket - exit the network namespace - after a moment (when the timewait socket is destroyed), the kernel panics. # BUG: unable to handle kernel NULL pointer dereference at 0000000000000007 IP: [] inet_twdr_do_twkill_work+0x6e/0xb8 PGD 119985067 PUD 11c5c0067 PMD 0 Oops: 0000 [1] SMP CPU 1 Modules linked in: ipv6 button battery ac loop dm_mod tg3 libphy ext3 jbd edd fan thermal processor thermal_sys sg sata_svw libata dock serverworks sd_mod scsi_mod ide_disk ide_core [last unloaded: freq_table] Pid: 0, comm: swapper Not tainted 2.6.27-rc2 #3 RIP: 0010:[] [] inet_twdr_do_twkill_work+0x6e/0xb8 RSP: 0018:ffff88011ff7fed0 EFLAGS: 00010246 RAX: ffffffffffffffff RBX: ffffffff82339420 RCX: ffff88011ff7ff30 RDX: 0000000000000001 RSI: ffff88011a4d03c0 RDI: ffff88011ac2fc00 RBP: ffffffff823392e0 R08: 0000000000000000 R09: ffff88002802a200 R10: ffff8800a5c4b000 R11: ffffffff823e4080 R12: ffff88011ac2fc00 R13: 0000000000000001 R14: 0000000000000001 R15: 0000000000000000 FS: 0000000041cbd940(0000) GS:ffff8800bff839c0(0000) knlGS:0000000000000000 CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b CR2: 0000000000000007 CR3: 00000000bd87c000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process swapper (pid: 0, threadinfo ffff8800bff9e000, task ffff88011ff76690) Stack: ffffffff823392e0 0000000000000100 ffffffff821e3a3a 0000000000000008 0000000000000000 ffffffff821e3a61 ffff8800bff7c000 ffffffff8203c7e7 ffff88011ff7ff10 ffff88011ff7ff10 0000000000000021 ffffffff82351108 Call Trace: [] ? inet_twdr_hangman+0x0/0x9e [] ? inet_twdr_hangman+0x27/0x9e [] ? run_timer_softirq+0x12c/0x193 [] ? __do_softirq+0x5e/0xcd [] ? call_softirq+0x1c/0x28 [] ? do_softirq+0x2c/0x68 [] ? smp_apic_timer_interrupt+0x8e/0xa9 [] ? apic_timer_interrupt+0x66/0x70 [] ? default_idle+0x27/0x3b [] ? cpu_idle+0x5f/0x7d Code: e8 01 00 00 4c 89 e7 41 ff c5 e8 8d fd ff ff 49 8b 44 24 38 4c 89 e7 65 8b 14 25 24 00 00 00 89 d2 48 8b 80 e8 00 00 00 48 f7 d0 <48> 8b 04 d0 48 ff 40 58 e8 fc fc ff ff 48 89 df e8 c0 5f 04 00 RIP [] inet_twdr_do_twkill_work+0x6e/0xb8 RSP CR2: 0000000000000007 This patch provides a function to purge all timewait sockets related to a network namespace. The timewait sockets life cycle is not tied with the network namespace, that means the timewait sockets stay alive while the network namespace dies. The timewait sockets are for avoiding to receive a duplicate packet from the network, if the network namespace is freed, the network stack is removed, so no chance to receive any packets from the outside world. Furthermore, having a pending destruction timer on these sockets with a network namespace freed is not safe and will lead to an oops if the timer callback which try to access data belonging to the namespace like for example in: inet_twdr_do_twkill_work -> NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED); Purging the timewait sockets at the network namespace destruction will: 1) speed up memory freeing for the namespace 2) fix kernel panic on asynchronous timewait destruction Signed-off-by: Daniel Lezcano Acked-by: Denis V. Lunev Acked-by: Eric W. Biederman Signed-off-by: David S. Miller --- include/net/inet_timewait_sock.h | 3 +++ net/ipv4/inet_timewait_sock.c | 35 ++++++++++++++++++++++++++++++++ net/ipv4/tcp_ipv4.c | 1 + net/ipv6/tcp_ipv6.c | 1 + 4 files changed, 40 insertions(+) diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h index 95c660c9719b..91324908fccd 100644 --- a/include/net/inet_timewait_sock.h +++ b/include/net/inet_timewait_sock.h @@ -208,6 +208,9 @@ extern void inet_twsk_schedule(struct inet_timewait_sock *tw, extern void inet_twsk_deschedule(struct inet_timewait_sock *tw, struct inet_timewait_death_row *twdr); +extern void inet_twsk_purge(struct net *net, struct inet_hashinfo *hashinfo, + struct inet_timewait_death_row *twdr, int family); + static inline struct net *twsk_net(const struct inet_timewait_sock *twsk) { diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c index d985bd613d25..743f011b9a84 100644 --- a/net/ipv4/inet_timewait_sock.c +++ b/net/ipv4/inet_timewait_sock.c @@ -409,3 +409,38 @@ out: } EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick); + +void inet_twsk_purge(struct net *net, struct inet_hashinfo *hashinfo, + struct inet_timewait_death_row *twdr, int family) +{ + struct inet_timewait_sock *tw; + struct sock *sk; + struct hlist_node *node; + int h; + + local_bh_disable(); + for (h = 0; h < (hashinfo->ehash_size); h++) { + struct inet_ehash_bucket *head = + inet_ehash_bucket(hashinfo, h); + rwlock_t *lock = inet_ehash_lockp(hashinfo, h); +restart: + write_lock(lock); + sk_for_each(sk, node, &head->twchain) { + + tw = inet_twsk(sk); + if (!net_eq(twsk_net(tw), net) || + tw->tw_family != family) + continue; + + atomic_inc(&tw->tw_refcnt); + write_unlock(lock); + inet_twsk_deschedule(tw, twdr); + inet_twsk_put(tw); + + goto restart; + } + write_unlock(lock); + } + local_bh_enable(); +} +EXPORT_SYMBOL_GPL(inet_twsk_purge); diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 44c1e934824b..1b4fee20fc93 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -2376,6 +2376,7 @@ static int __net_init tcp_sk_init(struct net *net) static void __net_exit tcp_sk_exit(struct net *net) { inet_ctl_sock_destroy(net->ipv4.tcp_sock); + inet_twsk_purge(net, &tcp_hashinfo, &tcp_death_row, AF_INET); } static struct pernet_operations __net_initdata tcp_sk_ops = { diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 5b90b369ccb2..b585c850a89a 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -2148,6 +2148,7 @@ static int tcpv6_net_init(struct net *net) static void tcpv6_net_exit(struct net *net) { inet_ctl_sock_destroy(net->ipv6.tcp_sk); + inet_twsk_purge(net, &tcp_hashinfo, &tcp_death_row, AF_INET6); } static struct pernet_operations tcpv6_net_ops = { -- 2.20.1