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kernel-ark/net/sched/cls_api.c
Patrick McHardy 85670cc1fa [NET_SCHED]: Fix fallout from dev->qdisc RCU change 
The move of qdisc destruction to a rcu callback broke locking in the
entire qdisc layer by invalidating previously valid assumptions about
the context in which changes to the qdisc tree occur.

The two assumptions were:

- since changes only happen in process context, read_lock doesn't need
  bottem half protection. Now invalid since destruction of inner qdiscs,
  classifiers, actions and estimators happens in the RCU callback unless
  they're manually deleted, resulting in dead-locks when read_lock in
  process context is interrupted by write_lock_bh in bottem half context.

- since changes only happen under the RTNL, no additional locking is
  necessary for data not used during packet processing (f.e. u32_list).
  Again, since destruction now happens in the RCU callback, this assumption
  is not valid anymore, causing races while using this data, which can
  result in corruption or use-after-free.

Instead of "fixing" this by disabling bottem halfs everywhere and adding
new locks/refcounting, this patch makes these assumptions valid again by
moving destruction back to process context. Since only the dev->qdisc
pointer is protected by RCU, but ->enqueue and the qdisc tree are still
protected by dev->qdisc_lock, destruction of the tree can be performed
immediately and only the final free needs to happen in the rcu callback
to make sure dev_queue_xmit doesn't access already freed memory.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-09-28 18:01:50 -07:00

643 lines
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/*
* net/sched/cls_api.c Packet classifier API.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
*
* Changes:
*
* Eduardo J. Blanco <ejbs@netlabs.com.uy> :990222: kmod support
*
*/
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <net/sock.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#if 0 /* control */
#define DPRINTK(format,args...) printk(KERN_DEBUG format,##args)
#else
#define DPRINTK(format,args...)
#endif
/* The list of all installed classifier types */
static struct tcf_proto_ops *tcf_proto_base;
/* Protects list of registered TC modules. It is pure SMP lock. */
static DEFINE_RWLOCK(cls_mod_lock);
/* Find classifier type by string name */
static struct tcf_proto_ops * tcf_proto_lookup_ops(struct rtattr *kind)
{
struct tcf_proto_ops *t = NULL;
if (kind) {
read_lock(&cls_mod_lock);
for (t = tcf_proto_base; t; t = t->next) {
if (rtattr_strcmp(kind, t->kind) == 0) {
if (!try_module_get(t->owner))
t = NULL;
break;
}
}
read_unlock(&cls_mod_lock);
}
return t;
}
/* Register(unregister) new classifier type */
int register_tcf_proto_ops(struct tcf_proto_ops *ops)
{
struct tcf_proto_ops *t, **tp;
int rc = -EEXIST;
write_lock(&cls_mod_lock);
for (tp = &tcf_proto_base; (t = *tp) != NULL; tp = &t->next)
if (!strcmp(ops->kind, t->kind))
goto out;
ops->next = NULL;
*tp = ops;
rc = 0;
out:
write_unlock(&cls_mod_lock);
return rc;
}
int unregister_tcf_proto_ops(struct tcf_proto_ops *ops)
{
struct tcf_proto_ops *t, **tp;
int rc = -ENOENT;
write_lock(&cls_mod_lock);
for (tp = &tcf_proto_base; (t=*tp) != NULL; tp = &t->next)
if (t == ops)
break;
if (!t)
goto out;
*tp = t->next;
rc = 0;
out:
write_unlock(&cls_mod_lock);
return rc;
}
static int tfilter_notify(struct sk_buff *oskb, struct nlmsghdr *n,
struct tcf_proto *tp, unsigned long fh, int event);
/* Select new prio value from the range, managed by kernel. */
static __inline__ u32 tcf_auto_prio(struct tcf_proto *tp)
{
u32 first = TC_H_MAKE(0xC0000000U,0U);
if (tp)
first = tp->prio-1;
return first;
}
/* Add/change/delete/get a filter node */
static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
{
struct rtattr **tca;
struct tcmsg *t;
u32 protocol;
u32 prio;
u32 nprio;
u32 parent;
struct net_device *dev;
struct Qdisc *q;
struct tcf_proto **back, **chain;
struct tcf_proto *tp;
struct tcf_proto_ops *tp_ops;
struct Qdisc_class_ops *cops;
unsigned long cl;
unsigned long fh;
int err;
replay:
tca = arg;
t = NLMSG_DATA(n);
protocol = TC_H_MIN(t->tcm_info);
prio = TC_H_MAJ(t->tcm_info);
nprio = prio;
parent = t->tcm_parent;
cl = 0;
if (prio == 0) {
/* If no priority is given, user wants we allocated it. */
if (n->nlmsg_type != RTM_NEWTFILTER || !(n->nlmsg_flags&NLM_F_CREATE))
return -ENOENT;
prio = TC_H_MAKE(0x80000000U,0U);
}
/* Find head of filter chain. */
/* Find link */
if ((dev = __dev_get_by_index(t->tcm_ifindex)) == NULL)
return -ENODEV;
/* Find qdisc */
if (!parent) {
q = dev->qdisc_sleeping;
parent = q->handle;
} else if ((q = qdisc_lookup(dev, TC_H_MAJ(t->tcm_parent))) == NULL)
return -EINVAL;
/* Is it classful? */
if ((cops = q->ops->cl_ops) == NULL)
return -EINVAL;
/* Do we search for filter, attached to class? */
if (TC_H_MIN(parent)) {
cl = cops->get(q, parent);
if (cl == 0)
return -ENOENT;
}
/* And the last stroke */
chain = cops->tcf_chain(q, cl);
err = -EINVAL;
if (chain == NULL)
goto errout;
/* Check the chain for existence of proto-tcf with this priority */
for (back = chain; (tp=*back) != NULL; back = &tp->next) {
if (tp->prio >= prio) {
if (tp->prio == prio) {
if (!nprio || (tp->protocol != protocol && protocol))
goto errout;
} else
tp = NULL;
break;
}
}
if (tp == NULL) {
/* Proto-tcf does not exist, create new one */
if (tca[TCA_KIND-1] == NULL || !protocol)
goto errout;
err = -ENOENT;
if (n->nlmsg_type != RTM_NEWTFILTER || !(n->nlmsg_flags&NLM_F_CREATE))
goto errout;
/* Create new proto tcf */
err = -ENOBUFS;
if ((tp = kmalloc(sizeof(*tp), GFP_KERNEL)) == NULL)
goto errout;
err = -EINVAL;
tp_ops = tcf_proto_lookup_ops(tca[TCA_KIND-1]);
if (tp_ops == NULL) {
#ifdef CONFIG_KMOD
struct rtattr *kind = tca[TCA_KIND-1];
char name[IFNAMSIZ];
if (kind != NULL &&
rtattr_strlcpy(name, kind, IFNAMSIZ) < IFNAMSIZ) {
rtnl_unlock();
request_module("cls_%s", name);
rtnl_lock();
tp_ops = tcf_proto_lookup_ops(kind);
/* We dropped the RTNL semaphore in order to
* perform the module load. So, even if we
* succeeded in loading the module we have to
* replay the request. We indicate this using
* -EAGAIN.
*/
if (tp_ops != NULL) {
module_put(tp_ops->owner);
err = -EAGAIN;
}
}
#endif
kfree(tp);
goto errout;
}
memset(tp, 0, sizeof(*tp));
tp->ops = tp_ops;
tp->protocol = protocol;
tp->prio = nprio ? : tcf_auto_prio(*back);
tp->q = q;
tp->classify = tp_ops->classify;
tp->classid = parent;
if ((err = tp_ops->init(tp)) != 0) {
module_put(tp_ops->owner);
kfree(tp);
goto errout;
}
qdisc_lock_tree(dev);
tp->next = *back;
*back = tp;
qdisc_unlock_tree(dev);
} else if (tca[TCA_KIND-1] && rtattr_strcmp(tca[TCA_KIND-1], tp->ops->kind))
goto errout;
fh = tp->ops->get(tp, t->tcm_handle);
if (fh == 0) {
if (n->nlmsg_type == RTM_DELTFILTER && t->tcm_handle == 0) {
qdisc_lock_tree(dev);
*back = tp->next;
qdisc_unlock_tree(dev);
tfilter_notify(skb, n, tp, fh, RTM_DELTFILTER);
tcf_destroy(tp);
err = 0;
goto errout;
}
err = -ENOENT;
if (n->nlmsg_type != RTM_NEWTFILTER || !(n->nlmsg_flags&NLM_F_CREATE))
goto errout;
} else {
switch (n->nlmsg_type) {
case RTM_NEWTFILTER:
err = -EEXIST;
if (n->nlmsg_flags&NLM_F_EXCL)
goto errout;
break;
case RTM_DELTFILTER:
err = tp->ops->delete(tp, fh);
if (err == 0)
tfilter_notify(skb, n, tp, fh, RTM_DELTFILTER);
goto errout;
case RTM_GETTFILTER:
err = tfilter_notify(skb, n, tp, fh, RTM_NEWTFILTER);
goto errout;
default:
err = -EINVAL;
goto errout;
}
}
err = tp->ops->change(tp, cl, t->tcm_handle, tca, &fh);
if (err == 0)
tfilter_notify(skb, n, tp, fh, RTM_NEWTFILTER);
errout:
if (cl)
cops->put(q, cl);
if (err == -EAGAIN)
/* Replay the request. */
goto replay;
return err;
}
static int
tcf_fill_node(struct sk_buff *skb, struct tcf_proto *tp, unsigned long fh,
u32 pid, u32 seq, u16 flags, int event)
{
struct tcmsg *tcm;
struct nlmsghdr *nlh;
unsigned char *b = skb->tail;
nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags);
tcm = NLMSG_DATA(nlh);
tcm->tcm_family = AF_UNSPEC;
tcm->tcm__pad1 = 0;
tcm->tcm__pad1 = 0;
tcm->tcm_ifindex = tp->q->dev->ifindex;
tcm->tcm_parent = tp->classid;
tcm->tcm_info = TC_H_MAKE(tp->prio, tp->protocol);
RTA_PUT(skb, TCA_KIND, IFNAMSIZ, tp->ops->kind);
tcm->tcm_handle = fh;
if (RTM_DELTFILTER != event) {
tcm->tcm_handle = 0;
if (tp->ops->dump && tp->ops->dump(tp, fh, skb, tcm) < 0)
goto rtattr_failure;
}
nlh->nlmsg_len = skb->tail - b;
return skb->len;
nlmsg_failure:
rtattr_failure:
skb_trim(skb, b - skb->data);
return -1;
}
static int tfilter_notify(struct sk_buff *oskb, struct nlmsghdr *n,
struct tcf_proto *tp, unsigned long fh, int event)
{
struct sk_buff *skb;
u32 pid = oskb ? NETLINK_CB(oskb).pid : 0;
skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
if (!skb)
return -ENOBUFS;
if (tcf_fill_node(skb, tp, fh, pid, n->nlmsg_seq, 0, event) <= 0) {
kfree_skb(skb);
return -EINVAL;
}
return rtnetlink_send(skb, pid, RTNLGRP_TC, n->nlmsg_flags&NLM_F_ECHO);
}
struct tcf_dump_args
{
struct tcf_walker w;
struct sk_buff *skb;
struct netlink_callback *cb;
};
static int tcf_node_dump(struct tcf_proto *tp, unsigned long n, struct tcf_walker *arg)
{
struct tcf_dump_args *a = (void*)arg;
return tcf_fill_node(a->skb, tp, n, NETLINK_CB(a->cb->skb).pid,
a->cb->nlh->nlmsg_seq, NLM_F_MULTI, RTM_NEWTFILTER);
}
static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
{
int t;
int s_t;
struct net_device *dev;
struct Qdisc *q;
struct tcf_proto *tp, **chain;
struct tcmsg *tcm = (struct tcmsg*)NLMSG_DATA(cb->nlh);
unsigned long cl = 0;
struct Qdisc_class_ops *cops;
struct tcf_dump_args arg;
if (cb->nlh->nlmsg_len < NLMSG_LENGTH(sizeof(*tcm)))
return skb->len;
if ((dev = dev_get_by_index(tcm->tcm_ifindex)) == NULL)
return skb->len;
read_lock(&qdisc_tree_lock);
if (!tcm->tcm_parent)
q = dev->qdisc_sleeping;
else
q = qdisc_lookup(dev, TC_H_MAJ(tcm->tcm_parent));
if (!q)
goto out;
if ((cops = q->ops->cl_ops) == NULL)
goto errout;
if (TC_H_MIN(tcm->tcm_parent)) {
cl = cops->get(q, tcm->tcm_parent);
if (cl == 0)
goto errout;
}
chain = cops->tcf_chain(q, cl);
if (chain == NULL)
goto errout;
s_t = cb->args[0];
for (tp=*chain, t=0; tp; tp = tp->next, t++) {
if (t < s_t) continue;
if (TC_H_MAJ(tcm->tcm_info) &&
TC_H_MAJ(tcm->tcm_info) != tp->prio)
continue;
if (TC_H_MIN(tcm->tcm_info) &&
TC_H_MIN(tcm->tcm_info) != tp->protocol)
continue;
if (t > s_t)
memset(&cb->args[1], 0, sizeof(cb->args)-sizeof(cb->args[0]));
if (cb->args[1] == 0) {
if (tcf_fill_node(skb, tp, 0, NETLINK_CB(cb->skb).pid,
cb->nlh->nlmsg_seq, NLM_F_MULTI, RTM_NEWTFILTER) <= 0) {
break;
}
cb->args[1] = 1;
}
if (tp->ops->walk == NULL)
continue;
arg.w.fn = tcf_node_dump;
arg.skb = skb;
arg.cb = cb;
arg.w.stop = 0;
arg.w.skip = cb->args[1]-1;
arg.w.count = 0;
tp->ops->walk(tp, &arg.w);
cb->args[1] = arg.w.count+1;
if (arg.w.stop)
break;
}
cb->args[0] = t;
errout:
if (cl)
cops->put(q, cl);
out:
read_unlock(&qdisc_tree_lock);
dev_put(dev);
return skb->len;
}
void
tcf_exts_destroy(struct tcf_proto *tp, struct tcf_exts *exts)
{
#ifdef CONFIG_NET_CLS_ACT
if (exts->action) {
tcf_action_destroy(exts->action, TCA_ACT_UNBIND);
exts->action = NULL;
}
#elif defined CONFIG_NET_CLS_POLICE
if (exts->police) {
tcf_police_release(exts->police, TCA_ACT_UNBIND);
exts->police = NULL;
}
#endif
}
int
tcf_exts_validate(struct tcf_proto *tp, struct rtattr **tb,
struct rtattr *rate_tlv, struct tcf_exts *exts,
struct tcf_ext_map *map)
{
memset(exts, 0, sizeof(*exts));
#ifdef CONFIG_NET_CLS_ACT
{
int err;
struct tc_action *act;
if (map->police && tb[map->police-1]) {
act = tcf_action_init_1(tb[map->police-1], rate_tlv, "police",
TCA_ACT_NOREPLACE, TCA_ACT_BIND, &err);
if (act == NULL)
return err;
act->type = TCA_OLD_COMPAT;
exts->action = act;
} else if (map->action && tb[map->action-1]) {
act = tcf_action_init(tb[map->action-1], rate_tlv, NULL,
TCA_ACT_NOREPLACE, TCA_ACT_BIND, &err);
if (act == NULL)
return err;
exts->action = act;
}
}
#elif defined CONFIG_NET_CLS_POLICE
if (map->police && tb[map->police-1]) {
struct tcf_police *p;
p = tcf_police_locate(tb[map->police-1], rate_tlv);
if (p == NULL)
return -EINVAL;
exts->police = p;
} else if (map->action && tb[map->action-1])
return -EOPNOTSUPP;
#else
if ((map->action && tb[map->action-1]) ||
(map->police && tb[map->police-1]))
return -EOPNOTSUPP;
#endif
return 0;
}
void
tcf_exts_change(struct tcf_proto *tp, struct tcf_exts *dst,
struct tcf_exts *src)
{
#ifdef CONFIG_NET_CLS_ACT
if (src->action) {
struct tc_action *act;
tcf_tree_lock(tp);
act = xchg(&dst->action, src->action);
tcf_tree_unlock(tp);
if (act)
tcf_action_destroy(act, TCA_ACT_UNBIND);
}
#elif defined CONFIG_NET_CLS_POLICE
if (src->police) {
struct tcf_police *p;
tcf_tree_lock(tp);
p = xchg(&dst->police, src->police);
tcf_tree_unlock(tp);
if (p)
tcf_police_release(p, TCA_ACT_UNBIND);
}
#endif
}
int
tcf_exts_dump(struct sk_buff *skb, struct tcf_exts *exts,
struct tcf_ext_map *map)
{
#ifdef CONFIG_NET_CLS_ACT
if (map->action && exts->action) {
/*
* again for backward compatible mode - we want
* to work with both old and new modes of entering
* tc data even if iproute2 was newer - jhs
*/
struct rtattr * p_rta = (struct rtattr*) skb->tail;
if (exts->action->type != TCA_OLD_COMPAT) {
RTA_PUT(skb, map->action, 0, NULL);
if (tcf_action_dump(skb, exts->action, 0, 0) < 0)
goto rtattr_failure;
p_rta->rta_len = skb->tail - (u8*)p_rta;
} else if (map->police) {
RTA_PUT(skb, map->police, 0, NULL);
if (tcf_action_dump_old(skb, exts->action, 0, 0) < 0)
goto rtattr_failure;
p_rta->rta_len = skb->tail - (u8*)p_rta;
}
}
#elif defined CONFIG_NET_CLS_POLICE
if (map->police && exts->police) {
struct rtattr * p_rta = (struct rtattr*) skb->tail;
RTA_PUT(skb, map->police, 0, NULL);
if (tcf_police_dump(skb, exts->police) < 0)
goto rtattr_failure;
p_rta->rta_len = skb->tail - (u8*)p_rta;
}
#endif
return 0;
rtattr_failure: __attribute__ ((unused))
return -1;
}
int
tcf_exts_dump_stats(struct sk_buff *skb, struct tcf_exts *exts,
struct tcf_ext_map *map)
{
#ifdef CONFIG_NET_CLS_ACT
if (exts->action)
if (tcf_action_copy_stats(skb, exts->action, 1) < 0)
goto rtattr_failure;
#elif defined CONFIG_NET_CLS_POLICE
if (exts->police)
if (tcf_police_dump_stats(skb, exts->police) < 0)
goto rtattr_failure;
#endif
return 0;
rtattr_failure: __attribute__ ((unused))
return -1;
}
static int __init tc_filter_init(void)
{
struct rtnetlink_link *link_p = rtnetlink_links[PF_UNSPEC];
/* Setup rtnetlink links. It is made here to avoid
exporting large number of public symbols.
*/
if (link_p) {
link_p[RTM_NEWTFILTER-RTM_BASE].doit = tc_ctl_tfilter;
link_p[RTM_DELTFILTER-RTM_BASE].doit = tc_ctl_tfilter;
link_p[RTM_GETTFILTER-RTM_BASE].doit = tc_ctl_tfilter;
link_p[RTM_GETTFILTER-RTM_BASE].dumpit = tc_dump_tfilter;
}
return 0;
}
subsys_initcall(tc_filter_init);
EXPORT_SYMBOL(register_tcf_proto_ops);
EXPORT_SYMBOL(unregister_tcf_proto_ops);
EXPORT_SYMBOL(tcf_exts_validate);
EXPORT_SYMBOL(tcf_exts_destroy);
EXPORT_SYMBOL(tcf_exts_change);
EXPORT_SYMBOL(tcf_exts_dump);
EXPORT_SYMBOL(tcf_exts_dump_stats);
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