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net: sched: unlock rules update API
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Register netlink protocol handlers for message types RTM_NEWTFILTER,
RTM_DELTFILTER, RTM_GETTFILTER as unlocked. Set rtnl_held variable that
tracks rtnl mutex state to be false by default.

Introduce tcf_proto_is_unlocked() helper that is used to check
tcf_proto_ops->flag to determine if ops can be called without taking rtnl
lock. Manually lookup Qdisc, class and block in rule update handlers.
Verify that both Qdisc ops and proto ops are unlocked before using any of
their callbacks, and obtain rtnl lock otherwise.

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 18d3eef commit 470502d
Showing 1 changed file with 114 additions and 17 deletions.
131 changes: 114 additions & 17 deletions net/sched/cls_api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -163,6 +163,23 @@ static inline u32 tcf_auto_prio(struct tcf_proto *tp)
return TC_H_MAJ(first);
}

static bool tcf_proto_is_unlocked(const char *kind)
{
const struct tcf_proto_ops *ops;
bool ret;

ops = tcf_proto_lookup_ops(kind, false, NULL);
/* On error return false to take rtnl lock. Proto lookup/create
* functions will perform lookup again and properly handle errors.
*/
if (IS_ERR(ops))
return false;

ret = !!(ops->flags & TCF_PROTO_OPS_DOIT_UNLOCKED);
module_put(ops->owner);
return ret;
}

static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
u32 prio, struct tcf_chain *chain,
bool rtnl_held,
Expand Down Expand Up @@ -1312,8 +1329,12 @@ static void tcf_block_release(struct Qdisc *q, struct tcf_block *block,
if (!IS_ERR_OR_NULL(block))
tcf_block_refcnt_put(block, rtnl_held);

if (q)
qdisc_put(q);
if (q) {
if (rtnl_held)
qdisc_put(q);
else
qdisc_put_unlocked(q);
}
}

struct tcf_block_owner_item {
Expand Down Expand Up @@ -1966,7 +1987,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
void *fh;
int err;
int tp_created;
bool rtnl_held = true;
bool rtnl_held = false;

if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
return -EPERM;
Expand All @@ -1985,6 +2006,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
parent = t->tcm_parent;
tp = NULL;
cl = 0;
block = NULL;

if (prio == 0) {
/* If no priority is provided by the user,
Expand All @@ -2001,8 +2023,27 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,

/* Find head of filter chain. */

block = tcf_block_find(net, &q, &parent, &cl,
t->tcm_ifindex, t->tcm_block_index, extack);
err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
if (err)
return err;

/* Take rtnl mutex if rtnl_held was set to true on previous iteration,
* block is shared (no qdisc found), qdisc is not unlocked, classifier
* type is not specified, classifier is not unlocked.
*/
if (rtnl_held ||
(q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
!tca[TCA_KIND] || !tcf_proto_is_unlocked(nla_data(tca[TCA_KIND]))) {
rtnl_held = true;
rtnl_lock();
}

err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
if (err)
goto errout;

block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
extack);
if (IS_ERR(block)) {
err = PTR_ERR(block);
goto errout;
Expand Down Expand Up @@ -2123,9 +2164,18 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
tcf_chain_put(chain);
}
tcf_block_release(q, block, rtnl_held);
if (err == -EAGAIN)

if (rtnl_held)
rtnl_unlock();

if (err == -EAGAIN) {
/* Take rtnl lock in case EAGAIN is caused by concurrent flush
* of target chain.
*/
rtnl_held = true;
/* Replay the request. */
goto replay;
}
return err;

errout_locked:
Expand All @@ -2146,12 +2196,12 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
struct Qdisc *q = NULL;
struct tcf_chain_info chain_info;
struct tcf_chain *chain = NULL;
struct tcf_block *block;
struct tcf_block *block = NULL;
struct tcf_proto *tp = NULL;
unsigned long cl = 0;
void *fh = NULL;
int err;
bool rtnl_held = true;
bool rtnl_held = false;

if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
return -EPERM;
Expand All @@ -2172,8 +2222,27 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,

/* Find head of filter chain. */

block = tcf_block_find(net, &q, &parent, &cl,
t->tcm_ifindex, t->tcm_block_index, extack);
err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
if (err)
return err;

/* Take rtnl mutex if flushing whole chain, block is shared (no qdisc
* found), qdisc is not unlocked, classifier type is not specified,
* classifier is not unlocked.
*/
if (!prio ||
(q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
!tca[TCA_KIND] || !tcf_proto_is_unlocked(nla_data(tca[TCA_KIND]))) {
rtnl_held = true;
rtnl_lock();
}

err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
if (err)
goto errout;

block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
extack);
if (IS_ERR(block)) {
err = PTR_ERR(block);
goto errout;
Expand Down Expand Up @@ -2255,6 +2324,10 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
tcf_chain_put(chain);
}
tcf_block_release(q, block, rtnl_held);

if (rtnl_held)
rtnl_unlock();

return err;

errout_locked:
Expand All @@ -2275,12 +2348,12 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
struct Qdisc *q = NULL;
struct tcf_chain_info chain_info;
struct tcf_chain *chain = NULL;
struct tcf_block *block;
struct tcf_block *block = NULL;
struct tcf_proto *tp = NULL;
unsigned long cl = 0;
void *fh = NULL;
int err;
bool rtnl_held = true;
bool rtnl_held = false;

err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, rtm_tca_policy, extack);
if (err < 0)
Expand All @@ -2298,8 +2371,26 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,

/* Find head of filter chain. */

block = tcf_block_find(net, &q, &parent, &cl,
t->tcm_ifindex, t->tcm_block_index, extack);
err = __tcf_qdisc_find(net, &q, &parent, t->tcm_ifindex, false, extack);
if (err)
return err;

/* Take rtnl mutex if block is shared (no qdisc found), qdisc is not
* unlocked, classifier type is not specified, classifier is not
* unlocked.
*/
if ((q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
!tca[TCA_KIND] || !tcf_proto_is_unlocked(nla_data(tca[TCA_KIND]))) {
rtnl_held = true;
rtnl_lock();
}

err = __tcf_qdisc_cl_find(q, parent, &cl, t->tcm_ifindex, extack);
if (err)
goto errout;

block = __tcf_block_find(net, q, cl, t->tcm_ifindex, t->tcm_block_index,
extack);
if (IS_ERR(block)) {
err = PTR_ERR(block);
goto errout;
Expand Down Expand Up @@ -2352,6 +2443,10 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
tcf_chain_put(chain);
}
tcf_block_release(q, block, rtnl_held);

if (rtnl_held)
rtnl_unlock();

return err;
}

Expand Down Expand Up @@ -3214,10 +3309,12 @@ static int __init tc_filter_init(void)
if (err)
goto err_rhash_setup_block_ht;

rtnl_register(PF_UNSPEC, RTM_NEWTFILTER, tc_new_tfilter, NULL, 0);
rtnl_register(PF_UNSPEC, RTM_DELTFILTER, tc_del_tfilter, NULL, 0);
rtnl_register(PF_UNSPEC, RTM_NEWTFILTER, tc_new_tfilter, NULL,
RTNL_FLAG_DOIT_UNLOCKED);
rtnl_register(PF_UNSPEC, RTM_DELTFILTER, tc_del_tfilter, NULL,
RTNL_FLAG_DOIT_UNLOCKED);
rtnl_register(PF_UNSPEC, RTM_GETTFILTER, tc_get_tfilter,
tc_dump_tfilter, 0);
tc_dump_tfilter, RTNL_FLAG_DOIT_UNLOCKED);
rtnl_register(PF_UNSPEC, RTM_NEWCHAIN, tc_ctl_chain, NULL, 0);
rtnl_register(PF_UNSPEC, RTM_DELCHAIN, tc_ctl_chain, NULL, 0);
rtnl_register(PF_UNSPEC, RTM_GETCHAIN, tc_ctl_chain,
Expand Down

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