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    Subject[PATCH tip/core/rcu 05/13] net: add checking to rcu_dereference() primitives
    Date
    Update rcu_dereference() primitives to use new lockdep-based checking.
    The rcu_dereference() in __in6_dev_get() may be protected either by
    rcu_read_lock() or RTNL, per Eric Dumazet. The rcu_dereference()
    in __sk_free() is protected by the fact that it is never reached if an
    update could change it. Check for this by using rcu_dereference_check()
    to verify that the struct sock's ->sk_wmem_alloc counter is zero.

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    include/linux/rtnetlink.h | 3 +++
    include/net/addrconf.h | 4 +++-
    net/core/dev.c | 2 +-
    net/core/filter.c | 6 +++---
    net/core/rtnetlink.c | 8 ++++++++
    net/core/sock.c | 3 ++-
    net/decnet/dn_route.c | 14 +++++++-------
    net/ipv4/route.c | 14 +++++++-------
    net/packet/af_packet.c | 2 +-
    9 files changed, 35 insertions(+), 21 deletions(-)

    diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
    index 05330fc..5c52fa4 100644
    --- a/include/linux/rtnetlink.h
    +++ b/include/linux/rtnetlink.h
    @@ -735,6 +735,9 @@ extern void rtnl_lock(void);
    extern void rtnl_unlock(void);
    extern int rtnl_trylock(void);
    extern int rtnl_is_locked(void);
    +#ifdef CONFIG_PROVE_LOCKING
    +extern int lockdep_rtnl_is_held(void);
    +#endif /* #ifdef CONFIG_PROVE_LOCKING */

    extern void rtnetlink_init(void);
    extern void __rtnl_unlock(void);
    diff --git a/include/net/addrconf.h b/include/net/addrconf.h
    index 0f7c378..45375b4 100644
    --- a/include/net/addrconf.h
    +++ b/include/net/addrconf.h
    @@ -177,7 +177,9 @@ extern int unregister_inet6addr_notifier(struct notifier_block *nb);
    static inline struct inet6_dev *
    __in6_dev_get(struct net_device *dev)
    {
    - return rcu_dereference(dev->ip6_ptr);
    + return rcu_dereference_check(dev->ip6_ptr,
    + rcu_read_lock_held() ||
    + lockdep_rtnl_is_held());
    }

    static inline struct inet6_dev *
    diff --git a/net/core/dev.c b/net/core/dev.c
    index be9924f..0d0ff82 100644
    --- a/net/core/dev.c
    +++ b/net/core/dev.c
    @@ -2041,7 +2041,7 @@ gso:
    rcu_read_lock_bh();

    txq = dev_pick_tx(dev, skb);
    - q = rcu_dereference(txq->qdisc);
    + q = rcu_dereference_bh(txq->qdisc);

    #ifdef CONFIG_NET_CLS_ACT
    skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_EGRESS);
    diff --git a/net/core/filter.c b/net/core/filter.c
    index 08db7b9..3541aa4 100644
    --- a/net/core/filter.c
    +++ b/net/core/filter.c
    @@ -86,7 +86,7 @@ int sk_filter(struct sock *sk, struct sk_buff *skb)
    return err;

    rcu_read_lock_bh();
    - filter = rcu_dereference(sk->sk_filter);
    + filter = rcu_dereference_bh(sk->sk_filter);
    if (filter) {
    unsigned int pkt_len = sk_run_filter(skb, filter->insns,
    filter->len);
    @@ -521,7 +521,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
    }

    rcu_read_lock_bh();
    - old_fp = rcu_dereference(sk->sk_filter);
    + old_fp = rcu_dereference_bh(sk->sk_filter);
    rcu_assign_pointer(sk->sk_filter, fp);
    rcu_read_unlock_bh();

    @@ -536,7 +536,7 @@ int sk_detach_filter(struct sock *sk)
    struct sk_filter *filter;

    rcu_read_lock_bh();
    - filter = rcu_dereference(sk->sk_filter);
    + filter = rcu_dereference_bh(sk->sk_filter);
    if (filter) {
    rcu_assign_pointer(sk->sk_filter, NULL);
    sk_filter_delayed_uncharge(sk, filter);
    diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
    index 794bcb8..4c7d3f6 100644
    --- a/net/core/rtnetlink.c
    +++ b/net/core/rtnetlink.c
    @@ -89,6 +89,14 @@ int rtnl_is_locked(void)
    }
    EXPORT_SYMBOL(rtnl_is_locked);

    +#ifdef CONFIG_PROVE_LOCKING
    +int lockdep_rtnl_is_held(void)
    +{
    + return lockdep_is_held(&rtnl_mutex);
    +}
    +EXPORT_SYMBOL(lockdep_rtnl_is_held);
    +#endif /* #ifdef CONFIG_PROVE_LOCKING */
    +
    static struct rtnl_link *rtnl_msg_handlers[NPROTO];

    static inline int rtm_msgindex(int msgtype)
    diff --git a/net/core/sock.c b/net/core/sock.c
    index e1f6f22..305cba4 100644
    --- a/net/core/sock.c
    +++ b/net/core/sock.c
    @@ -1073,7 +1073,8 @@ static void __sk_free(struct sock *sk)
    if (sk->sk_destruct)
    sk->sk_destruct(sk);

    - filter = rcu_dereference(sk->sk_filter);
    + filter = rcu_dereference_check(sk->sk_filter,
    + atomic_read(&sk->sk_wmem_alloc) == 0);
    if (filter) {
    sk_filter_uncharge(sk, filter);
    rcu_assign_pointer(sk->sk_filter, NULL);
    diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
    index a032840..a7bf03c 100644
    --- a/net/decnet/dn_route.c
    +++ b/net/decnet/dn_route.c
    @@ -1155,8 +1155,8 @@ static int __dn_route_output_key(struct dst_entry **pprt, const struct flowi *fl

    if (!(flags & MSG_TRYHARD)) {
    rcu_read_lock_bh();
    - for(rt = rcu_dereference(dn_rt_hash_table[hash].chain); rt;
    - rt = rcu_dereference(rt->u.dst.dn_next)) {
    + for (rt = rcu_dereference_bh(dn_rt_hash_table[hash].chain); rt;
    + rt = rcu_dereference_bh(rt->u.dst.dn_next)) {
    if ((flp->fld_dst == rt->fl.fld_dst) &&
    (flp->fld_src == rt->fl.fld_src) &&
    (flp->mark == rt->fl.mark) &&
    @@ -1618,9 +1618,9 @@ int dn_cache_dump(struct sk_buff *skb, struct netlink_callback *cb)
    if (h > s_h)
    s_idx = 0;
    rcu_read_lock_bh();
    - for(rt = rcu_dereference(dn_rt_hash_table[h].chain), idx = 0;
    + for(rt = rcu_dereference_bh(dn_rt_hash_table[h].chain), idx = 0;
    rt;
    - rt = rcu_dereference(rt->u.dst.dn_next), idx++) {
    + rt = rcu_dereference_bh(rt->u.dst.dn_next), idx++) {
    if (idx < s_idx)
    continue;
    skb_dst_set(skb, dst_clone(&rt->u.dst));
    @@ -1654,12 +1654,12 @@ static struct dn_route *dn_rt_cache_get_first(struct seq_file *seq)

    for(s->bucket = dn_rt_hash_mask; s->bucket >= 0; --s->bucket) {
    rcu_read_lock_bh();
    - rt = dn_rt_hash_table[s->bucket].chain;
    + rt = rcu_dereference_bh(dn_rt_hash_table[s->bucket].chain);
    if (rt)
    break;
    rcu_read_unlock_bh();
    }
    - return rcu_dereference(rt);
    + return rt;
    }

    static struct dn_route *dn_rt_cache_get_next(struct seq_file *seq, struct dn_route *rt)
    @@ -1674,7 +1674,7 @@ static struct dn_route *dn_rt_cache_get_next(struct seq_file *seq, struct dn_rou
    rcu_read_lock_bh();
    rt = dn_rt_hash_table[s->bucket].chain;
    }
    - return rcu_dereference(rt);
    + return rcu_dereference_bh(rt);
    }

    static void *dn_rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
    diff --git a/net/ipv4/route.c b/net/ipv4/route.c
    index e446496..3476b3b 100644
    --- a/net/ipv4/route.c
    +++ b/net/ipv4/route.c
    @@ -287,12 +287,12 @@ static struct rtable *rt_cache_get_first(struct seq_file *seq)
    if (!rt_hash_table[st->bucket].chain)
    continue;
    rcu_read_lock_bh();
    - r = rcu_dereference(rt_hash_table[st->bucket].chain);
    + r = rcu_dereference_bh(rt_hash_table[st->bucket].chain);
    while (r) {
    if (dev_net(r->u.dst.dev) == seq_file_net(seq) &&
    r->rt_genid == st->genid)
    return r;
    - r = rcu_dereference(r->u.dst.rt_next);
    + r = rcu_dereference_bh(r->u.dst.rt_next);
    }
    rcu_read_unlock_bh();
    }
    @@ -314,7 +314,7 @@ static struct rtable *__rt_cache_get_next(struct seq_file *seq,
    rcu_read_lock_bh();
    r = rt_hash_table[st->bucket].chain;
    }
    - return rcu_dereference(r);
    + return rcu_dereference_bh(r);
    }

    static struct rtable *rt_cache_get_next(struct seq_file *seq,
    @@ -2687,8 +2687,8 @@ int __ip_route_output_key(struct net *net, struct rtable **rp,
    hash = rt_hash(flp->fl4_dst, flp->fl4_src, flp->oif, rt_genid(net));

    rcu_read_lock_bh();
    - for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
    - rth = rcu_dereference(rth->u.dst.rt_next)) {
    + for (rth = rcu_dereference_bh(rt_hash_table[hash].chain); rth;
    + rth = rcu_dereference_bh(rth->u.dst.rt_next)) {
    if (rth->fl.fl4_dst == flp->fl4_dst &&
    rth->fl.fl4_src == flp->fl4_src &&
    rth->fl.iif == 0 &&
    @@ -3006,8 +3006,8 @@ int ip_rt_dump(struct sk_buff *skb, struct netlink_callback *cb)
    if (!rt_hash_table[h].chain)
    continue;
    rcu_read_lock_bh();
    - for (rt = rcu_dereference(rt_hash_table[h].chain), idx = 0; rt;
    - rt = rcu_dereference(rt->u.dst.rt_next), idx++) {
    + for (rt = rcu_dereference_bh(rt_hash_table[h].chain), idx = 0; rt;
    + rt = rcu_dereference_bh(rt->u.dst.rt_next), idx++) {
    if (!net_eq(dev_net(rt->u.dst.dev), net) || idx < s_idx)
    continue;
    if (rt_is_expired(rt))
    diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
    index f126d18..939471e 100644
    --- a/net/packet/af_packet.c
    +++ b/net/packet/af_packet.c
    @@ -508,7 +508,7 @@ static inline unsigned int run_filter(struct sk_buff *skb, struct sock *sk,
    struct sk_filter *filter;

    rcu_read_lock_bh();
    - filter = rcu_dereference(sk->sk_filter);
    + filter = rcu_dereference_bh(sk->sk_filter);
    if (filter != NULL)
    res = sk_run_filter(skb, filter->insns, filter->len);
    rcu_read_unlock_bh();
    --
    1.6.6


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