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Martin KaFai Lau says:

====================
ipv6: Fix dst_entry refcnt bugs in ip6_tunnel

v4:
- Fix a compilation error in patch 5 when CONFIG_LOCKDEP is turned on and
  re-test it

v3:
- Merge a 'if else if' test in patch 4
- Use rcu_dereference_protected in patch 5 to fix a sparse check when
  CONFIG_SPARSE_RCU_POINTER is enabled

v2:
- Add patch 4 and 5 to remove the spinlock

v1:
This patch series is to fix the dst refcnt bugs in ip6_tunnel.

Patch 1 and 2 are the prep works.  Patch 3 is the fix.

I can reproduce the bug by adding and removing the ip6gre tunnel
while running a super_netperf TCP_CRR test.  I get the following
trace by adding WARN_ON_ONCE(newrefcnt < 0) to dst_release():

[  312.760432] ------------[ cut here ]------------
[  312.774664] WARNING: CPU: 2 PID: 10263 at net/core/dst.c:288 dst_release+0xf3/0x100()
[  312.776041] Modules linked in: k10temp coretemp hwmon ip6_gre ip6_tunnel tunnel6 ipmi_devintf ipmi_ms\
ghandler ip6table_filter ip6_tables xt_NFLOG nfnetlink_log nfnetlink xt_comment xt_statistic iptable_fil\
ter ip_tables x_tables nfsv3 nfs_acl nfs fscache lockd grace mptctl netconsole autofs4 rpcsec_gss_krb5 a\
uth_rpcgss oid_registry sunrpc ipv6 dm_mod loop iTCO_wdt iTCO_vendor_support serio_raw rtc_cmos pcspkr i\
2c_i801 i2c_core lpc_ich mfd_core ehci_pci ehci_hcd e1000e mlx4_en ptp pps_core vxlan udp_tunnel ip6_udp\
_tunnel mlx4_core sg button ext3 jbd mpt2sas raid_class
[  312.785302] CPU: 2 PID: 10263 Comm: netperf Not tainted 4.2.0-rc8-00046-g4db9b63-dirty #15
[  312.791695] Hardware name: Quanta Freedom /Windmill-EP, BIOS F03_3B04 09/12/2013
[  312.792965]  ffffffff819dca2c ffff8811dfbdf6f8 ffffffff816537de ffff88123788fdb8
[  312.794263]  0000000000000000 ffff8811dfbdf738 ffffffff81052646 ffff8811dfbdf768
[  312.795593]  ffff881203a98180 00000000ffffffff ffff88242927a000 ffff88120a2532e0
[  312.796946] Call Trace:
[  312.797380]  [<ffffffff816537de>] dump_stack+0x45/0x57
[  312.798288]  [<ffffffff81052646>] warn_slowpath_common+0x86/0xc0
[  312.799699]  [<ffffffff8105273a>] warn_slowpath_null+0x1a/0x20
[  312.800852]  [<ffffffff8159f9b3>] dst_release+0xf3/0x100
[  312.801834]  [<ffffffffa03f1308>] ip6_tnl_dst_store+0x48/0x70 [ip6_tunnel]
[  312.803738]  [<ffffffffa03fd0b6>] ip6gre_xmit2+0x536/0x720 [ip6_gre]
[  312.804774]  [<ffffffffa03fd40a>] ip6gre_tunnel_xmit+0x16a/0x410 [ip6_gre]
[  312.805986]  [<ffffffff8159934b>] dev_hard_start_xmit+0x23b/0x390
[  312.808810]  [<ffffffff815a2f5f>] ? neigh_destroy+0xef/0x140
[  312.809843]  [<ffffffff81599a6c>] __dev_queue_xmit+0x48c/0x4f0
[  312.813931]  [<ffffffff81599ae3>] dev_queue_xmit_sk+0x13/0x20
[  312.814993]  [<ffffffff815a0832>] neigh_direct_output+0x12/0x20
[  312.817448]  [<ffffffffa021d633>] ip6_finish_output2+0x183/0x460 [ipv6]
[  312.818762]  [<ffffffff81306fc5>] ? find_next_bit+0x15/0x20
[  312.819671]  [<ffffffffa021fd79>] ip6_finish_output+0x89/0xe0 [ipv6]
[  312.820720]  [<ffffffffa021fe14>] ip6_output+0x44/0xe0 [ipv6]
[  312.821762]  [<ffffffff815c8809>] ? nf_hook_slow+0x69/0xc0
[  312.823123]  [<ffffffffa021d232>] ip6_xmit+0x242/0x4c0 [ipv6]
[  312.824073]  [<ffffffffa021c9f0>] ? ac6_proc_exit+0x20/0x20 [ipv6]
[  312.825116]  [<ffffffffa024c751>] inet6_csk_xmit+0x61/0xa0 [ipv6]
[  312.826127]  [<ffffffff815eb590>] tcp_transmit_skb+0x4f0/0x9b0
[  312.827441]  [<ffffffff815ed267>] tcp_connect+0x637/0x7a0
[  312.828327]  [<ffffffffa0245906>] tcp_v6_connect+0x2d6/0x550 [ipv6]
[  312.829581]  [<ffffffff81606f05>] __inet_stream_connect+0x95/0x2f0
[  312.830600]  [<ffffffff810ae13a>] ? hrtimer_try_to_cancel+0x1a/0xf0
[  312.833456]  [<ffffffff812fba19>] ? timerqueue_add+0x59/0xb0
[  312.834407]  [<ffffffff81607198>] inet_stream_connect+0x38/0x50
[  312.835886]  [<ffffffff8157cb17>] SYSC_connect+0xb7/0xf0
[  312.840035]  [<ffffffff810af6d3>] ? do_setitimer+0x1b3/0x200
[  312.840983]  [<ffffffff810af75a>] ? alarm_setitimer+0x3a/0x70
[  312.841941]  [<ffffffff8157d7ae>] SyS_connect+0xe/0x10
[  312.842818]  [<ffffffff81659297>] entry_SYSCALL_64_fastpath+0x12/0x6a
[  312.844206] ---[ end trace 43f3ecd86c3b1313 ]---
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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@davem330
davem330 committed Sep 15, 2015
2 parents e8684c8 + 70da5b5 commit 244b7f4
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Showing 6 changed files with 179 additions and 78 deletions.
15 changes: 11 additions & 4 deletions include/net/ip6_tunnel.h
View file
Expand Up @@ -32,15 +32,20 @@ struct __ip6_tnl_parm {
__be32 o_key;
};

struct ip6_tnl_dst {
seqlock_t lock;
struct dst_entry __rcu *dst;
u32 cookie;
};

/* IPv6 tunnel */
struct ip6_tnl {
struct ip6_tnl __rcu *next; /* next tunnel in list */
struct net_device *dev; /* virtual device associated with tunnel */
struct net *net; /* netns for packet i/o */
struct __ip6_tnl_parm parms; /* tunnel configuration parameters */
struct flowi fl; /* flowi template for xmit */
struct dst_entry *dst_cache; /* cached dst */
u32 dst_cookie;
struct ip6_tnl_dst __percpu *dst_cache; /* cached dst */

int err_count;
unsigned long err_time;
Expand All @@ -60,9 +65,11 @@ struct ipv6_tlv_tnl_enc_lim {
__u8 encap_limit; /* tunnel encapsulation limit */
} __packed;

struct dst_entry *ip6_tnl_dst_check(struct ip6_tnl *t);
struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t);
int ip6_tnl_dst_init(struct ip6_tnl *t);
void ip6_tnl_dst_destroy(struct ip6_tnl *t);
void ip6_tnl_dst_reset(struct ip6_tnl *t);
void ip6_tnl_dst_store(struct ip6_tnl *t, struct dst_entry *dst);
void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst);
int ip6_tnl_rcv_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,
const struct in6_addr *raddr);
int ip6_tnl_xmit_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,
Expand Down
7 changes: 3 additions & 4 deletions net/ipv6/addrconf.c
View file
Expand Up @@ -5127,13 +5127,12 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)

rt = addrconf_get_prefix_route(&ifp->peer_addr, 128,
ifp->idev->dev, 0, 0);
if (rt && ip6_del_rt(rt))
dst_free(&rt->dst);
if (rt)
ip6_del_rt(rt);
}
dst_hold(&ifp->rt->dst);

if (ip6_del_rt(ifp->rt))
dst_free(&ifp->rt->dst);
ip6_del_rt(ifp->rt);

rt_genid_bump_ipv6(net);
break;
Expand Down
20 changes: 16 additions & 4 deletions net/ipv6/ip6_fib.c
View file
Expand Up @@ -155,6 +155,11 @@ static void node_free(struct fib6_node *fn)
kmem_cache_free(fib6_node_kmem, fn);
}

static void rt6_rcu_free(struct rt6_info *rt)
{
call_rcu(&rt->dst.rcu_head, dst_rcu_free);
}

static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
{
int cpu;
Expand All @@ -169,7 +174,7 @@ static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
ppcpu_rt = per_cpu_ptr(non_pcpu_rt->rt6i_pcpu, cpu);
pcpu_rt = *ppcpu_rt;
if (pcpu_rt) {
dst_free(&pcpu_rt->dst);
rt6_rcu_free(pcpu_rt);
*ppcpu_rt = NULL;
}
}
Expand All @@ -181,7 +186,7 @@ static void rt6_release(struct rt6_info *rt)
{
if (atomic_dec_and_test(&rt->rt6i_ref)) {
rt6_free_pcpu(rt);
dst_free(&rt->dst);
rt6_rcu_free(rt);
}
}

Expand Down Expand Up @@ -933,6 +938,10 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
int replace_required = 0;
int sernum = fib6_new_sernum(info->nl_net);

if (WARN_ON_ONCE((rt->dst.flags & DST_NOCACHE) &&
!atomic_read(&rt->dst.__refcnt)))
return -EINVAL;

if (info->nlh) {
if (!(info->nlh->nlmsg_flags & NLM_F_CREATE))
allow_create = 0;
Expand Down Expand Up @@ -1025,6 +1034,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
fib6_start_gc(info->nl_net, rt);
if (!(rt->rt6i_flags & RTF_CACHE))
fib6_prune_clones(info->nl_net, pn);
rt->dst.flags &= ~DST_NOCACHE;
}

out:
Expand All @@ -1049,7 +1059,8 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
atomic_inc(&pn->leaf->rt6i_ref);
}
#endif
dst_free(&rt->dst);
if (!(rt->dst.flags & DST_NOCACHE))
dst_free(&rt->dst);
}
return err;

Expand All @@ -1060,7 +1071,8 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
st_failure:
if (fn && !(fn->fn_flags & (RTN_RTINFO|RTN_ROOT)))
fib6_repair_tree(info->nl_net, fn);
dst_free(&rt->dst);
if (!(rt->dst.flags & DST_NOCACHE))
dst_free(&rt->dst);
return err;
#endif
}
Expand Down
77 changes: 47 additions & 30 deletions net/ipv6/ip6_gre.c
View file
Expand Up @@ -634,20 +634,20 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
}

if (!fl6->flowi6_mark)
dst = ip6_tnl_dst_check(tunnel);
dst = ip6_tnl_dst_get(tunnel);

if (!dst) {
ndst = ip6_route_output(net, NULL, fl6);
dst = ip6_route_output(net, NULL, fl6);

if (ndst->error)
if (dst->error)
goto tx_err_link_failure;
ndst = xfrm_lookup(net, ndst, flowi6_to_flowi(fl6), NULL, 0);
if (IS_ERR(ndst)) {
err = PTR_ERR(ndst);
ndst = NULL;
dst = xfrm_lookup(net, dst, flowi6_to_flowi(fl6), NULL, 0);
if (IS_ERR(dst)) {
err = PTR_ERR(dst);
dst = NULL;
goto tx_err_link_failure;
}
dst = ndst;
ndst = dst;
}

tdev = dst->dev;
Expand Down Expand Up @@ -702,12 +702,9 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
skb = new_skb;
}

if (fl6->flowi6_mark) {
skb_dst_set(skb, dst);
ndst = NULL;
} else {
skb_dst_set_noref(skb, dst);
}
if (!fl6->flowi6_mark && ndst)
ip6_tnl_dst_set(tunnel, ndst);
skb_dst_set(skb, dst);

proto = NEXTHDR_GRE;
if (encap_limit >= 0) {
Expand Down Expand Up @@ -762,14 +759,12 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb,
skb_set_inner_protocol(skb, protocol);

ip6tunnel_xmit(NULL, skb, dev);
if (ndst)
ip6_tnl_dst_store(tunnel, ndst);
return 0;
tx_err_link_failure:
stats->tx_carrier_errors++;
dst_link_failure(skb);
tx_err_dst_release:
dst_release(ndst);
dst_release(dst);
return err;
}

Expand Down Expand Up @@ -1223,6 +1218,9 @@ static const struct net_device_ops ip6gre_netdev_ops = {

static void ip6gre_dev_free(struct net_device *dev)
{
struct ip6_tnl *t = netdev_priv(dev);

ip6_tnl_dst_destroy(t);
free_percpu(dev->tstats);
free_netdev(dev);
}
Expand All @@ -1245,26 +1243,48 @@ static void ip6gre_tunnel_setup(struct net_device *dev)
netif_keep_dst(dev);
}

static int ip6gre_tunnel_init(struct net_device *dev)
static int ip6gre_tunnel_init_common(struct net_device *dev)
{
struct ip6_tnl *tunnel;
int ret;

tunnel = netdev_priv(dev);

tunnel->dev = dev;
tunnel->net = dev_net(dev);
strcpy(tunnel->parms.name, dev->name);

dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
if (!dev->tstats)
return -ENOMEM;

ret = ip6_tnl_dst_init(tunnel);
if (ret) {
free_percpu(dev->tstats);
dev->tstats = NULL;
return ret;
}

return 0;
}

static int ip6gre_tunnel_init(struct net_device *dev)
{
struct ip6_tnl *tunnel;
int ret;

ret = ip6gre_tunnel_init_common(dev);
if (ret)
return ret;

tunnel = netdev_priv(dev);

memcpy(dev->dev_addr, &tunnel->parms.laddr, sizeof(struct in6_addr));
memcpy(dev->broadcast, &tunnel->parms.raddr, sizeof(struct in6_addr));

if (ipv6_addr_any(&tunnel->parms.raddr))
dev->header_ops = &ip6gre_header_ops;

dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
if (!dev->tstats)
return -ENOMEM;

return 0;
}

Expand Down Expand Up @@ -1460,19 +1480,16 @@ static void ip6gre_netlink_parms(struct nlattr *data[],
static int ip6gre_tap_init(struct net_device *dev)
{
struct ip6_tnl *tunnel;
int ret;

tunnel = netdev_priv(dev);
ret = ip6gre_tunnel_init_common(dev);
if (ret)
return ret;

tunnel->dev = dev;
tunnel->net = dev_net(dev);
strcpy(tunnel->parms.name, dev->name);
tunnel = netdev_priv(dev);

ip6gre_tnl_link_config(tunnel, 1);

dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
if (!dev->tstats)
return -ENOMEM;

return 0;
}

Expand Down

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