From: Vlad Buslov <vladbu@xxxxxxxxxxxx> [ Upstream commit e368fdb61d8e7c67ac70791b23345b26d7bbc661 ] As a preparation from removing rtnl lock dependency from rules update path, use Qdisc rcu and reference counting capabilities instead of relying on rtnl lock while working with Qdiscs. Create new tcf_block_release() function, and use it to free resources taken by tcf_block_find(). Currently, this function only releases Qdisc and it is extended in next patches in this series. Signed-off-by: Vlad Buslov <vladbu@xxxxxxxxxxxx> Acked-by: Jiri Pirko <jiri@xxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> [Lee: Sent to Stable] Link: https://syzkaller.appspot.com/bug?id=d7e411c5472dd5da33d8cc921ccadc747743a568 Reported-by: syzbot+5f229e48cccc804062c0@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/sched/cls_api.c | 79 ++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 64 insertions(+), 15 deletions(-) --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -539,6 +539,7 @@ static struct tcf_block *tcf_block_find( struct netlink_ext_ack *extack) { struct tcf_block *block; + int err = 0; if (ifindex == TCM_IFINDEX_MAGIC_BLOCK) { block = tcf_block_lookup(net, block_index); @@ -550,55 +551,93 @@ static struct tcf_block *tcf_block_find( const struct Qdisc_class_ops *cops; struct net_device *dev; + rcu_read_lock(); + /* Find link */ - dev = __dev_get_by_index(net, ifindex); - if (!dev) + dev = dev_get_by_index_rcu(net, ifindex); + if (!dev) { + rcu_read_unlock(); return ERR_PTR(-ENODEV); + } /* Find qdisc */ if (!*parent) { *q = dev->qdisc; *parent = (*q)->handle; } else { - *q = qdisc_lookup(dev, TC_H_MAJ(*parent)); + *q = qdisc_lookup_rcu(dev, TC_H_MAJ(*parent)); if (!*q) { NL_SET_ERR_MSG(extack, "Parent Qdisc doesn't exists"); - return ERR_PTR(-EINVAL); + err = -EINVAL; + goto errout_rcu; } } + *q = qdisc_refcount_inc_nz(*q); + if (!*q) { + NL_SET_ERR_MSG(extack, "Parent Qdisc doesn't exists"); + err = -EINVAL; + goto errout_rcu; + } + /* Is it classful? */ cops = (*q)->ops->cl_ops; if (!cops) { NL_SET_ERR_MSG(extack, "Qdisc not classful"); - return ERR_PTR(-EINVAL); + err = -EINVAL; + goto errout_rcu; } if (!cops->tcf_block) { NL_SET_ERR_MSG(extack, "Class doesn't support blocks"); - return ERR_PTR(-EOPNOTSUPP); + err = -EOPNOTSUPP; + goto errout_rcu; } + /* At this point we know that qdisc is not noop_qdisc, + * which means that qdisc holds a reference to net_device + * and we hold a reference to qdisc, so it is safe to release + * rcu read lock. + */ + rcu_read_unlock(); + /* Do we search for filter, attached to class? */ if (TC_H_MIN(*parent)) { *cl = cops->find(*q, *parent); if (*cl == 0) { NL_SET_ERR_MSG(extack, "Specified class doesn't exist"); - return ERR_PTR(-ENOENT); + err = -ENOENT; + goto errout_qdisc; } } /* And the last stroke */ block = cops->tcf_block(*q, *cl, extack); - if (!block) - return ERR_PTR(-EINVAL); + if (!block) { + err = -EINVAL; + goto errout_qdisc; + } if (tcf_block_shared(block)) { NL_SET_ERR_MSG(extack, "This filter block is shared. Please use the block index to manipulate the filters"); - return ERR_PTR(-EOPNOTSUPP); + err = -EOPNOTSUPP; + goto errout_qdisc; } } return block; + +errout_rcu: + rcu_read_unlock(); +errout_qdisc: + if (*q) + qdisc_put(*q); + return ERR_PTR(err); +} + +static void tcf_block_release(struct Qdisc *q, struct tcf_block *block) +{ + if (q) + qdisc_put(q); } struct tcf_block_owner_item { @@ -1336,6 +1375,7 @@ replay: errout: if (chain) tcf_chain_put(chain); + tcf_block_release(q, block); if (err == -EAGAIN) /* Replay the request. */ goto replay; @@ -1457,6 +1497,7 @@ static int tc_del_tfilter(struct sk_buff errout: if (chain) tcf_chain_put(chain); + tcf_block_release(q, block); return err; } @@ -1542,6 +1583,7 @@ static int tc_get_tfilter(struct sk_buff errout: if (chain) tcf_chain_put(chain); + tcf_block_release(q, block); return err; } @@ -1858,7 +1900,8 @@ replay: chain_index = tca[TCA_CHAIN] ? nla_get_u32(tca[TCA_CHAIN]) : 0; if (chain_index > TC_ACT_EXT_VAL_MASK) { NL_SET_ERR_MSG(extack, "Specified chain index exceeds upper limit"); - return -EINVAL; + err = -EINVAL; + goto errout_block; } chain = tcf_chain_lookup(block, chain_index); if (n->nlmsg_type == RTM_NEWCHAIN) { @@ -1870,23 +1913,27 @@ replay: tcf_chain_hold(chain); } else { NL_SET_ERR_MSG(extack, "Filter chain already exists"); - return -EEXIST; + err = -EEXIST; + goto errout_block; } } else { if (!(n->nlmsg_flags & NLM_F_CREATE)) { NL_SET_ERR_MSG(extack, "Need both RTM_NEWCHAIN and NLM_F_CREATE to create a new chain"); - return -ENOENT; + err = -ENOENT; + goto errout_block; } chain = tcf_chain_create(block, chain_index); if (!chain) { NL_SET_ERR_MSG(extack, "Failed to create filter chain"); - return -ENOMEM; + err = -ENOMEM; + goto errout_block; } } } else { if (!chain || tcf_chain_held_by_acts_only(chain)) { NL_SET_ERR_MSG(extack, "Cannot find specified filter chain"); - return -EINVAL; + err = -EINVAL; + goto errout_block; } tcf_chain_hold(chain); } @@ -1930,6 +1977,8 @@ replay: errout: tcf_chain_put(chain); +errout_block: + tcf_block_release(q, block); if (err == -EAGAIN) /* Replay the request. */ goto replay;
