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authorMartin KaFai Lau <kafai@fb.com>2019-04-30 10:45:12 -0700
committerDavid S. Miller <davem@davemloft.net>2019-05-01 17:17:54 -0400
commit886b7a50100a50f1cbd08a6f8ec5884dfbe082dc (patch)
treef18e97f6f5ac9054af65539f00e52c6160470a20
parentf3505745c07ff50c22aeca9dde98762d1c8b5898 (diff)
download96b-common-886b7a50100a50f1cbd08a6f8ec5884dfbe082dc.tar.gz
ipv6: A few fixes on dereferencing rt->from
It is a followup after the fix in commit 9c69a1320515 ("route: Avoid crash from dereferencing NULL rt->from") rt6_do_redirect(): 1. NULL checking is needed on rt->from because a parallel fib6_info delete could happen that sets rt->from to NULL. (e.g. rt6_remove_exception() and fib6_drop_pcpu_from()). 2. fib6_info_hold() is not enough. Same reason as (1). Meaning, holding dst->__refcnt cannot ensure rt->from is not NULL or rt->from->fib6_ref is not 0. Instead of using fib6_info_hold_safe() which ip6_rt_cache_alloc() is already doing, this patch chooses to extend the rcu section to keep "from" dereference-able after checking for NULL. inet6_rtm_getroute(): 1. NULL checking is also needed on rt->from for a similar reason. Note that inet6_rtm_getroute() is using RTNL_FLAG_DOIT_UNLOCKED. Fixes: a68886a69180 ("net/ipv6: Make from in rt6_info rcu protected") Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Wei Wang <weiwan@google.com> Reviewed-by: David Ahern <dsahern@gmail.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv6/route.c38
1 files changed, 18 insertions, 20 deletions
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 2cc166bc978d..0520aca3354b 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3392,11 +3392,8 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
rcu_read_lock();
from = rcu_dereference(rt->from);
- /* This fib6_info_hold() is safe here because we hold reference to rt
- * and rt already holds reference to fib6_info.
- */
- fib6_info_hold(from);
- rcu_read_unlock();
+ if (!from)
+ goto out;
nrt = ip6_rt_cache_alloc(from, &msg->dest, NULL);
if (!nrt)
@@ -3408,10 +3405,7 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
nrt->rt6i_gateway = *(struct in6_addr *)neigh->primary_key;
- /* No need to remove rt from the exception table if rt is
- * a cached route because rt6_insert_exception() will
- * takes care of it
- */
+ /* rt6_insert_exception() will take care of duplicated exceptions */
if (rt6_insert_exception(nrt, from)) {
dst_release_immediate(&nrt->dst);
goto out;
@@ -3424,7 +3418,7 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
call_netevent_notifiers(NETEVENT_REDIRECT, &netevent);
out:
- fib6_info_release(from);
+ rcu_read_unlock();
neigh_release(neigh);
}
@@ -5023,16 +5017,20 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
rcu_read_lock();
from = rcu_dereference(rt->from);
-
- if (fibmatch)
- 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, from, dst, &fl6.daddr,
- &fl6.saddr, iif, RTM_NEWROUTE,
- NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
- 0);
+ if (from) {
+ if (fibmatch)
+ 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, from, dst, &fl6.daddr,
+ &fl6.saddr, iif, RTM_NEWROUTE,
+ NETLINK_CB(in_skb).portid,
+ nlh->nlmsg_seq, 0);
+ } else {
+ err = -ENETUNREACH;
+ }
rcu_read_unlock();
if (err < 0) {