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Commit a68886a6 authored by David Ahern's avatar David Ahern Committed by David S. Miller
Browse files

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: default avatarDavid Ahern <dsahern@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5bcaa41b

include/net/ip6_fib.h

+6 −4
Original line number Diff line number Diff line
@@ -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();

net/ipv6/ip6_fib.c

+6 −2
Original line number Diff line number Diff line
@@ -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);

		}

	}

}

net/ipv6/ip6_output.c

+7 −2
Original line number Diff line number Diff line
@@ -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;

net/ipv6/route.c

+69 −27
Original line number Diff line number Diff line
@@ -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);

			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;