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net/ipv6: Make from in rt6_info rcu protected 

When a dst entry is created from a fib entry, the 'from' in rt6_info
is set to the fib entry. The 'from' reference is used most notably for
cookie checking - making sure stale dst entries are updated if the
fib entry is changed.

When a fib entry is deleted, the pcpu routes on it are walked releasing
the fib6_info reference. This is needed for the fib6_info cleanup to
happen and to make sure all device references are released in a timely
manner.

There is a race window when a FIB entry is deleted and the 'from' on the
pcpu route is dropped and the pcpu route hits a cookie check. Handle
this race using rcu on from.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2018-04-20 15:38:02 -07:00 committed by David S. Miller
parent 5bcaa41b96
commit a68886a691
4 changed files with 88 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/net/ip6_fib.h
View File

@ -174,7 +174,7 @@ struct fib6_info {
struct rt6_info {
struct dst_entry dst;
struct fib6_info *from;
struct fib6_info __rcu *from;
struct rt6key rt6i_dst;
struct rt6key rt6i_src;
@ -248,13 +248,15 @@ static inline bool fib6_get_cookie_safe(const struct fib6_info *f6i,
static inline u32 rt6_get_cookie(const struct rt6_info *rt)
{
struct fib6_info *from;
u32 cookie = 0;
rcu_read_lock();
if (rt->rt6i_flags & RTF_PCPU ||
(unlikely(!list_empty(&rt->rt6i_uncached)) && rt->from))
fib6_get_cookie_safe(rt->from, &cookie);
from = rcu_dereference(rt->from);
if (from && (rt->rt6i_flags & RTF_PCPU ||
unlikely(!list_empty(&rt->rt6i_uncached))))
fib6_get_cookie_safe(from, &cookie);
rcu_read_unlock();

8
net/ipv6/ip6_fib.c
View File

@ -875,8 +875,12 @@ static void fib6_drop_pcpu_from(struct fib6_info *f6i,
ppcpu_rt = per_cpu_ptr(f6i->rt6i_pcpu, cpu);
pcpu_rt = *ppcpu_rt;
if (pcpu_rt) {
fib6_info_release(pcpu_rt->from);
pcpu_rt->from = NULL;
struct fib6_info *from;
from = rcu_dereference_protected(pcpu_rt->from,
lockdep_is_held(&table->tb6_lock));
rcu_assign_pointer(pcpu_rt->from, NULL);
fib6_info_release(from);
}
}
}

9
net/ipv6/ip6_output.c
View File

@ -962,16 +962,21 @@ static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,
* that's why we try it again later.
*/
if (ipv6_addr_any(&fl6->saddr) && (!*dst || !(*dst)->error)) {
struct fib6_info *from;
struct rt6_info *rt;
bool had_dst = *dst != NULL;
if (!had_dst)
*dst = ip6_route_output(net, sk, fl6);
rt = (*dst)->error ? NULL : (struct rt6_info *)*dst;
err = ip6_route_get_saddr(net, rt ? rt->from : NULL,
&fl6->daddr,
rcu_read_lock();
from = rt ? rcu_dereference(rt->from) : NULL;
err = ip6_route_get_saddr(net, from, &fl6->daddr,
sk ? inet6_sk(sk)->srcprefs : 0,
&fl6->saddr);
rcu_read_unlock();
if (err)
goto out_err_release;

96
net/ipv6/route.c
View File

@ -359,7 +359,7 @@ EXPORT_SYMBOL(ip6_dst_alloc);
static void ip6_dst_destroy(struct dst_entry *dst)
{
struct rt6_info *rt = (struct rt6_info *)dst;
struct fib6_info *from = rt->from;
struct fib6_info *from;
struct inet6_dev *idev;
dst_destroy_metrics_generic(dst);
@ -371,8 +371,11 @@ static void ip6_dst_destroy(struct dst_entry *dst)
in6_dev_put(idev);
}
rt->from = NULL;
rcu_read_lock();
from = rcu_dereference(rt->from);
rcu_assign_pointer(rt->from, NULL);
fib6_info_release(from);
rcu_read_unlock();
}
static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
@ -402,12 +405,16 @@ static bool __rt6_check_expired(const struct rt6_info *rt)
static bool rt6_check_expired(const struct rt6_info *rt)
{
struct fib6_info *from;
from = rcu_dereference(rt->from);
if (rt->rt6i_flags & RTF_EXPIRES) {
if (time_after(jiffies, rt->dst.expires))
return true;
} else if (rt->from) {
} else if (from) {
return rt->dst.obsolete != DST_OBSOLETE_FORCE_CHK ||
fib6_check_expired(rt->from);
fib6_check_expired(from);
}
return false;
}
@ -963,7 +970,7 @@ static void rt6_set_from(struct rt6_info *rt, struct fib6_info *from)
{
rt->rt6i_flags &= ~RTF_EXPIRES;
fib6_info_hold(from);
rt->from = from;
rcu_assign_pointer(rt->from, from);
dst_init_metrics(&rt->dst, from->fib6_metrics->metrics, true);
if (from->fib6_metrics != &dst_default_metrics) {
rt->dst._metrics |= DST_METRICS_REFCOUNTED;
@ -2133,11 +2140,13 @@ static bool fib6_check(struct fib6_info *f6i, u32 cookie)
return true;
}
static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie)
static struct dst_entry *rt6_check(struct rt6_info *rt,
struct fib6_info *from,
u32 cookie)
{
u32 rt_cookie = 0;
if ((rt->from && !fib6_get_cookie_safe(rt->from, &rt_cookie)) ||
if ((from && !fib6_get_cookie_safe(from, &rt_cookie)) ||
rt_cookie != cookie)
return NULL;
@ -2147,11 +2156,13 @@ static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie)
return &rt->dst;
}
static struct dst_entry *rt6_dst_from_check(struct rt6_info *rt, u32 cookie)
static struct dst_entry *rt6_dst_from_check(struct rt6_info *rt,
struct fib6_info *from,
u32 cookie)
{
if (!__rt6_check_expired(rt) &&
rt->dst.obsolete == DST_OBSOLETE_FORCE_CHK &&
fib6_check(rt->from, cookie))
fib6_check(from, cookie))
return &rt->dst;
else
return NULL;
@ -2160,6 +2171,7 @@ static struct dst_entry *rt6_dst_from_check(struct rt6_info *rt, u32 cookie)
static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie)
{
struct dst_entry *dst_ret;
struct fib6_info *from;
struct rt6_info *rt;
rt = container_of(dst, struct rt6_info, dst);
@ -2171,11 +2183,13 @@ static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie)
* into this function always.
*/
if (rt->rt6i_flags & RTF_PCPU ||
(unlikely(!list_empty(&rt->rt6i_uncached)) && rt->from))
dst_ret = rt6_dst_from_check(rt, cookie);
from = rcu_dereference(rt->from);
if (from && (rt->rt6i_flags & RTF_PCPU ||
unlikely(!list_empty(&rt->rt6i_uncached))))
dst_ret = rt6_dst_from_check(rt, from, cookie);
else
dst_ret = rt6_check(rt, cookie);
dst_ret = rt6_check(rt, from, cookie);
rcu_read_unlock();
@ -2211,13 +2225,17 @@ static void ip6_link_failure(struct sk_buff *skb)
if (rt->rt6i_flags & RTF_CACHE) {
if (dst_hold_safe(&rt->dst))
rt6_remove_exception_rt(rt);
} else if (rt->from) {
} else {
struct fib6_info *from;
struct fib6_node *fn;
rcu_read_lock();
fn = rcu_dereference(rt->from->fib6_node);
if (fn && (rt->rt6i_flags & RTF_DEFAULT))
fn->fn_sernum = -1;
from = rcu_dereference(rt->from);
if (from) {
fn = rcu_dereference(from->fib6_node);
if (fn && (rt->rt6i_flags & RTF_DEFAULT))
fn->fn_sernum = -1;
}
rcu_read_unlock();
}
}
@ -2225,8 +2243,15 @@ static void ip6_link_failure(struct sk_buff *skb)
static void rt6_update_expires(struct rt6_info *rt0, int timeout)
{
if (!(rt0->rt6i_flags & RTF_EXPIRES) && rt0->from)
rt0->dst.expires = rt0->from->expires;
if (!(rt0->rt6i_flags & RTF_EXPIRES)) {
struct fib6_info *from;
rcu_read_lock();
from = rcu_dereference(rt0->from);
if (from)
rt0->dst.expires = from->expires;
rcu_read_unlock();
}
dst_set_expires(&rt0->dst, timeout);
rt0->rt6i_flags |= RTF_EXPIRES;
@ -2243,8 +2268,14 @@ static void rt6_do_update_pmtu(struct rt6_info *rt, u32 mtu)
static bool rt6_cache_allowed_for_pmtu(const struct rt6_info *rt)
{
bool from_set;
rcu_read_lock();
from_set = !!rcu_dereference(rt->from);
rcu_read_unlock();
return !(rt->rt6i_flags & RTF_CACHE) &&
(rt->rt6i_flags & RTF_PCPU || rt->from);
(rt->rt6i_flags & RTF_PCPU || from_set);
}
static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
@ -2280,16 +2311,18 @@ static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
if (rt6->rt6i_flags & RTF_CACHE)
rt6_update_exception_stamp_rt(rt6);
} else if (daddr) {
struct fib6_info *from;
struct rt6_info *nrt6;
rcu_read_lock();
nrt6 = ip6_rt_cache_alloc(rt6->from, daddr, saddr);
rcu_read_unlock();
from = rcu_dereference(rt6->from);
nrt6 = ip6_rt_cache_alloc(from, daddr, saddr);
if (nrt6) {
rt6_do_update_pmtu(nrt6, mtu);
if (rt6_insert_exception(nrt6, rt6->from))
if (rt6_insert_exception(nrt6, from))
dst_release_immediate(&nrt6->dst);
}
rcu_read_unlock();
}
}
@ -3222,6 +3255,7 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
struct ndisc_options ndopts;
struct inet6_dev *in6_dev;
struct neighbour *neigh;
struct fib6_info *from;
struct rd_msg *msg;
int optlen, on_link;
u8 *lladdr;
@ -3304,7 +3338,8 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
NDISC_REDIRECT, &ndopts);
rcu_read_lock();
nrt = ip6_rt_cache_alloc(rt->from, &msg->dest, NULL);
from = rcu_dereference(rt->from);
nrt = ip6_rt_cache_alloc(from, &msg->dest, NULL);
rcu_read_unlock();
if (!nrt)
goto out;
@ -4687,6 +4722,7 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
struct net *net = sock_net(in_skb->sk);
struct nlattr *tb[RTA_MAX+1];
int err, iif = 0, oif = 0;
struct fib6_info *from;
struct dst_entry *dst;
struct rt6_info *rt;
struct sk_buff *skb;
@ -4783,15 +4819,21 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
}
skb_dst_set(skb, &rt->dst);
rcu_read_lock();
from = rcu_dereference(rt->from);
if (fibmatch)
err = rt6_fill_node(net, skb, rt->from, NULL, NULL, NULL, iif,
err = rt6_fill_node(net, skb, from, NULL, NULL, NULL, iif,
RTM_NEWROUTE, NETLINK_CB(in_skb).portid,
nlh->nlmsg_seq, 0);
else
err = rt6_fill_node(net, skb, rt->from, dst,
&fl6.daddr, &fl6.saddr, iif, RTM_NEWROUTE,
err = rt6_fill_node(net, skb, from, dst, &fl6.daddr,
&fl6.saddr, iif, RTM_NEWROUTE,
NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
0);
rcu_read_unlock();
if (err < 0) {
kfree_skb(skb);
goto errout;