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net: sched: protect filter_chain list with filter_chain_lock mutex
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Extend tcf_chain with new filter_chain_lock mutex. Always lock the chain
when accessing filter_chain list, instead of relying on rtnl lock.
Dereference filter_chain with tcf_chain_dereference() lockdep macro to
verify that all users of chain_list have the lock taken.

Rearrange tp insert/remove code in tc_new_tfilter/tc_del_tfilter to execute
all necessary code while holding chain lock in order to prevent
invalidation of chain_info structure by potential concurrent change. This
also serializes calls to tcf_chain0_head_change(), which allows head change
callbacks to rely on filter_chain_lock for synchronization instead of rtnl
mutex.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Vlad Buslov authored and David S. Miller committed Feb 12, 2019
1 parent a565482 commit ed76f5e
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Showing 3 changed files with 101 additions and 33 deletions.
17 changes: 17 additions & 0 deletions include/net/sch_generic.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -341,6 +341,8 @@ struct qdisc_skb_cb {
typedef void tcf_chain_head_change_t(struct tcf_proto *tp_head, void *priv);

struct tcf_chain {
/* Protects filter_chain. */
struct mutex filter_chain_lock;
struct tcf_proto __rcu *filter_chain;
struct list_head list;
struct tcf_block *block;
Expand Down Expand Up @@ -374,6 +376,21 @@ struct tcf_block {
struct rcu_head rcu;
};

#ifdef CONFIG_PROVE_LOCKING
static inline bool lockdep_tcf_chain_is_locked(struct tcf_chain *chain)
{
return lockdep_is_held(&chain->filter_chain_lock);
}
#else
static inline bool lockdep_tcf_chain_is_locked(struct tcf_block *chain)
{
return true;
}
#endif /* #ifdef CONFIG_PROVE_LOCKING */

#define tcf_chain_dereference(p, chain) \
rcu_dereference_protected(p, lockdep_tcf_chain_is_locked(chain))

static inline void tcf_block_offload_inc(struct tcf_block *block, u32 *flags)
{
if (*flags & TCA_CLS_FLAGS_IN_HW)
Expand Down
111 changes: 79 additions & 32 deletions net/sched/cls_api.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -221,6 +221,7 @@ static struct tcf_chain *tcf_chain_create(struct tcf_block *block,
if (!chain)
return NULL;
list_add_tail(&chain->list, &block->chain_list);
mutex_init(&chain->filter_chain_lock);
chain->block = block;
chain->index = chain_index;
chain->refcnt = 1;
Expand Down Expand Up @@ -280,6 +281,7 @@ static void tcf_chain_destroy(struct tcf_chain *chain, bool free_block)
{
struct tcf_block *block = chain->block;

mutex_destroy(&chain->filter_chain_lock);
kfree(chain);
if (free_block)
tcf_block_destroy(block);
Expand Down Expand Up @@ -443,9 +445,13 @@ static void tcf_chain_put_explicitly_created(struct tcf_chain *chain)

static void tcf_chain_flush(struct tcf_chain *chain)
{
struct tcf_proto *tp = rtnl_dereference(chain->filter_chain);
struct tcf_proto *tp;

mutex_lock(&chain->filter_chain_lock);
tp = tcf_chain_dereference(chain->filter_chain, chain);
tcf_chain0_head_change(chain, NULL);
mutex_unlock(&chain->filter_chain_lock);

while (tp) {
RCU_INIT_POINTER(chain->filter_chain, tp->next);
tcf_proto_destroy(tp, NULL);
Expand Down Expand Up @@ -785,11 +791,29 @@ tcf_chain0_head_change_cb_add(struct tcf_block *block,

mutex_lock(&block->lock);
chain0 = block->chain0.chain;
if (chain0 && chain0->filter_chain)
tcf_chain_head_change_item(item, chain0->filter_chain);
list_add(&item->list, &block->chain0.filter_chain_list);
if (chain0)
tcf_chain_hold(chain0);
else
list_add(&item->list, &block->chain0.filter_chain_list);
mutex_unlock(&block->lock);

if (chain0) {
struct tcf_proto *tp_head;

mutex_lock(&chain0->filter_chain_lock);

tp_head = tcf_chain_dereference(chain0->filter_chain, chain0);
if (tp_head)
tcf_chain_head_change_item(item, tp_head);

mutex_lock(&block->lock);
list_add(&item->list, &block->chain0.filter_chain_list);
mutex_unlock(&block->lock);

mutex_unlock(&chain0->filter_chain_lock);
tcf_chain_put(chain0);
}

return 0;
}

Expand Down Expand Up @@ -1464,9 +1488,10 @@ struct tcf_chain_info {
struct tcf_proto __rcu *next;
};

static struct tcf_proto *tcf_chain_tp_prev(struct tcf_chain_info *chain_info)
static struct tcf_proto *tcf_chain_tp_prev(struct tcf_chain *chain,
struct tcf_chain_info *chain_info)
{
return rtnl_dereference(*chain_info->pprev);
return tcf_chain_dereference(*chain_info->pprev, chain);
}

static void tcf_chain_tp_insert(struct tcf_chain *chain,
Expand All @@ -1475,7 +1500,7 @@ static void tcf_chain_tp_insert(struct tcf_chain *chain,
{
if (*chain_info->pprev == chain->filter_chain)
tcf_chain0_head_change(chain, tp);
RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain_info));
RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain, chain_info));
rcu_assign_pointer(*chain_info->pprev, tp);
tcf_chain_hold(chain);
}
Expand All @@ -1484,7 +1509,7 @@ static void tcf_chain_tp_remove(struct tcf_chain *chain,
struct tcf_chain_info *chain_info,
struct tcf_proto *tp)
{
struct tcf_proto *next = rtnl_dereference(chain_info->next);
struct tcf_proto *next = tcf_chain_dereference(chain_info->next, chain);

if (tp == chain->filter_chain)
tcf_chain0_head_change(chain, next);
Expand All @@ -1502,7 +1527,8 @@ static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain,

/* Check the chain for existence of proto-tcf with this priority */
for (pprev = &chain->filter_chain;
(tp = rtnl_dereference(*pprev)); pprev = &tp->next) {
(tp = tcf_chain_dereference(*pprev, chain));
pprev = &tp->next) {
if (tp->prio >= prio) {
if (tp->prio == prio) {
if (prio_allocate ||
Expand Down Expand Up @@ -1710,12 +1736,13 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
goto errout;
}

mutex_lock(&chain->filter_chain_lock);
tp = tcf_chain_tp_find(chain, &chain_info, protocol,
prio, prio_allocate);
if (IS_ERR(tp)) {
NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
err = PTR_ERR(tp);
goto errout;
goto errout_locked;
}

if (tp == NULL) {
Expand All @@ -1724,29 +1751,37 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
if (tca[TCA_KIND] == NULL || !protocol) {
NL_SET_ERR_MSG(extack, "Filter kind and protocol must be specified");
err = -EINVAL;
goto errout;
goto errout_locked;
}

if (!(n->nlmsg_flags & NLM_F_CREATE)) {
NL_SET_ERR_MSG(extack, "Need both RTM_NEWTFILTER and NLM_F_CREATE to create a new filter");
err = -ENOENT;
goto errout;
goto errout_locked;
}

if (prio_allocate)
prio = tcf_auto_prio(tcf_chain_tp_prev(&chain_info));
prio = tcf_auto_prio(tcf_chain_tp_prev(chain,
&chain_info));

mutex_unlock(&chain->filter_chain_lock);
tp = tcf_proto_create(nla_data(tca[TCA_KIND]),
protocol, prio, chain, extack);
if (IS_ERR(tp)) {
err = PTR_ERR(tp);
goto errout;
}

mutex_lock(&chain->filter_chain_lock);
tcf_chain_tp_insert(chain, &chain_info, tp);
mutex_unlock(&chain->filter_chain_lock);
tp_created = 1;
} else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
err = -EINVAL;
goto errout;
goto errout_locked;
} else {
mutex_unlock(&chain->filter_chain_lock);
}

fh = tp->ops->get(tp, t->tcm_handle);
Expand All @@ -1772,15 +1807,11 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
err = tp->ops->change(net, skb, tp, cl, t->tcm_handle, tca, &fh,
n->nlmsg_flags & NLM_F_CREATE ? TCA_ACT_NOREPLACE : TCA_ACT_REPLACE,
extack);
if (err == 0) {
if (tp_created)
tcf_chain_tp_insert(chain, &chain_info, tp);
if (err == 0)
tfilter_notify(net, skb, n, tp, block, q, parent, fh,
RTM_NEWTFILTER, false);
} else {
if (tp_created)
tcf_proto_destroy(tp, NULL);
}
else if (tp_created)
tcf_proto_destroy(tp, NULL);

errout:
if (chain)
Expand All @@ -1790,6 +1821,10 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
/* Replay the request. */
goto replay;
return err;

errout_locked:
mutex_unlock(&chain->filter_chain_lock);
goto errout;
}

static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
Expand Down Expand Up @@ -1865,31 +1900,34 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
goto errout;
}

mutex_lock(&chain->filter_chain_lock);
tp = tcf_chain_tp_find(chain, &chain_info, protocol,
prio, false);
if (!tp || IS_ERR(tp)) {
NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
err = tp ? PTR_ERR(tp) : -ENOENT;
goto errout;
goto errout_locked;
} else if (tca[TCA_KIND] && nla_strcmp(tca[TCA_KIND], tp->ops->kind)) {
NL_SET_ERR_MSG(extack, "Specified filter kind does not match existing one");
err = -EINVAL;
goto errout_locked;
} else if (t->tcm_handle == 0) {
tcf_chain_tp_remove(chain, &chain_info, tp);
mutex_unlock(&chain->filter_chain_lock);

tfilter_notify(net, skb, n, tp, block, q, parent, fh,
RTM_DELTFILTER, false);
tcf_proto_destroy(tp, extack);
err = 0;
goto errout;
}
mutex_unlock(&chain->filter_chain_lock);

fh = tp->ops->get(tp, t->tcm_handle);

if (!fh) {
if (t->tcm_handle == 0) {
tcf_chain_tp_remove(chain, &chain_info, tp);
tfilter_notify(net, skb, n, tp, block, q, parent, fh,
RTM_DELTFILTER, false);
tcf_proto_destroy(tp, extack);
err = 0;
} else {
NL_SET_ERR_MSG(extack, "Specified filter handle not found");
err = -ENOENT;
}
NL_SET_ERR_MSG(extack, "Specified filter handle not found");
err = -ENOENT;
} else {
bool last;

Expand All @@ -1899,7 +1937,10 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
if (err)
goto errout;
if (last) {
mutex_lock(&chain->filter_chain_lock);
tcf_chain_tp_remove(chain, &chain_info, tp);
mutex_unlock(&chain->filter_chain_lock);

tcf_proto_destroy(tp, extack);
}
}
Expand All @@ -1909,6 +1950,10 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
tcf_chain_put(chain);
tcf_block_release(q, block);
return err;

errout_locked:
mutex_unlock(&chain->filter_chain_lock);
goto errout;
}

static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
Expand Down Expand Up @@ -1966,8 +2011,10 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
goto errout;
}

mutex_lock(&chain->filter_chain_lock);
tp = tcf_chain_tp_find(chain, &chain_info, protocol,
prio, false);
mutex_unlock(&chain->filter_chain_lock);
if (!tp || IS_ERR(tp)) {
NL_SET_ERR_MSG(extack, "Filter with specified priority/protocol not found");
err = tp ? PTR_ERR(tp) : -ENOENT;
Expand Down
6 changes: 5 additions & 1 deletion net/sched/sch_generic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1366,7 +1366,11 @@ static void mini_qdisc_rcu_func(struct rcu_head *head)
void mini_qdisc_pair_swap(struct mini_Qdisc_pair *miniqp,
struct tcf_proto *tp_head)
{
struct mini_Qdisc *miniq_old = rtnl_dereference(*miniqp->p_miniq);
/* Protected with chain0->filter_chain_lock.
* Can't access chain directly because tp_head can be NULL.
*/
struct mini_Qdisc *miniq_old =
rcu_dereference_protected(*miniqp->p_miniq, 1);
struct mini_Qdisc *miniq;

if (!tp_head) {
Expand Down

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