| Message ID | 20180423183207.9124-3-dsahern@gmail.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | net/ipv6: couple of fixes for rcu change to from | expand |
On 04/23/2018 11:32 AM, David Ahern wrote: > 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: a68886a69180 ("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> > --- > net/ipv6/route.c | 15 ++++++++++----- > 1 file changed, 10 insertions(+), 5 deletions(-) > > diff --git a/net/ipv6/route.c b/net/ipv6/route.c > index 354a5b8d016f..ac3e51631c65 100644 > --- a/net/ipv6/route.c > +++ b/net/ipv6/route.c > @@ -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)); This does not make any sense. We lock rt6_exception_lock a bit later in this function (line 1558) If we really were holding rt6_exception_lock here we would dead lock. > if (!from || > !(rt->rt6i_flags & RTF_CACHE)) > return -EINVAL; > @@ -2223,6 +2225,7 @@ static void ip6_link_failure(struct sk_buff *skb)
On 04/24/2018 08:54 AM, Eric Dumazet wrote: > > > On 04/23/2018 11:32 AM, David Ahern wrote: >> 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: a68886a69180 ("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> >> --- >> net/ipv6/route.c | 15 ++++++++++----- >> 1 file changed, 10 insertions(+), 5 deletions(-) >> >> diff --git a/net/ipv6/route.c b/net/ipv6/route.c >> index 354a5b8d016f..ac3e51631c65 100644 >> --- a/net/ipv6/route.c >> +++ b/net/ipv6/route.c >> @@ -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)); > > This does not make any sense. > > We lock rt6_exception_lock a bit later in this function (line 1558) > > If we really were holding rt6_exception_lock here we would dead lock. I will send this fix : diff --git a/net/ipv6/route.c b/net/ipv6/route.c index ac3e51631c659b5c5c8a93c17011cb7f3ad266e2..432c4bcc1111085671f32987e4673e47898085a3 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1546,8 +1546,7 @@ static int rt6_remove_exception_rt(struct rt6_info *rt) struct fib6_info *from; int err; - from = rcu_dereference_protected(rt->from, - lockdep_is_held(&rt6_exception_lock)); + from = rcu_dereference(rt->from); if (!from || !(rt->rt6i_flags & RTF_CACHE)) return -EINVAL;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 354a5b8d016f..ac3e51631c65 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -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); }
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: a68886a69180 ("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> --- net/ipv6/route.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)