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net/ipv6: Fix missing rcu dereferences on from 

kbuild test robot reported 2 uses of rt->from not properly accessed
using rcu_dereference:
1. add rcu_dereference_protected to rt6_remove_exception_rt and make
   sure it is always called with rcu lock held.

2. change rt6_do_redirect to take a reference on 'from' when accessed
   the first time so it can be used the sceond time outside of the lock

Fixes: a68886a691 ("net/ipv6: Make from in rt6_info rcu protected")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
David Ahern 2018-04-23 11:32:07 -07:00 committed by David S. Miller
parent c3c14da028
commit 8a14e46f14
1 changed files with 10 additions and 5 deletions
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15
net/ipv6/route.c
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@ -1541,11 +1541,13 @@ static struct rt6_info *rt6_find_cached_rt(struct fib6_info *rt,
static int rt6_remove_exception_rt(struct rt6_info *rt)
{
struct rt6_exception_bucket *bucket;
struct fib6_info *from = rt->from;
struct in6_addr *src_key = NULL;
struct rt6_exception *rt6_ex;
struct fib6_info *from;
int err;
from = rcu_dereference_protected(rt->from,
lockdep_is_held(&rt6_exception_lock));
if (!from ||
!(rt->rt6i_flags & RTF_CACHE))
return -EINVAL;
@ -2223,6 +2225,7 @@ static void ip6_link_failure(struct sk_buff *skb)
rt = (struct rt6_info *) skb_dst(skb);
if (rt) {
rcu_read_lock();
if (rt->rt6i_flags & RTF_CACHE) {
if (dst_hold_safe(&rt->dst))
rt6_remove_exception_rt(rt);
@ -2230,15 +2233,14 @@ static void ip6_link_failure(struct sk_buff *skb)
struct fib6_info *from;
struct fib6_node *fn;
rcu_read_lock();
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();
}
rcu_read_unlock();
}
}
@ -3340,8 +3342,10 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
rcu_read_lock();
from = rcu_dereference(rt->from);
nrt = ip6_rt_cache_alloc(from, &msg->dest, NULL);
fib6_info_hold(from);
rcu_read_unlock();
nrt = ip6_rt_cache_alloc(from, &msg->dest, NULL);
if (!nrt)
goto out;
@ -3355,7 +3359,7 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
* a cached route because rt6_insert_exception() will
* takes care of it
*/
if (rt6_insert_exception(nrt, rt->from)) {
if (rt6_insert_exception(nrt, from)) {
dst_release_immediate(&nrt->dst);
goto out;
}
@ -3367,6 +3371,7 @@ 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);
neigh_release(neigh);
}