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linux/net/sched/cls_tcindex.c
Daniel Borkmann d936377414 net, sched: respect rcu grace period on cls destruction 
Roi reported a crash in flower where tp->root was NULL in ->classify()
callbacks. Reason is that in ->destroy() tp->root is set to NULL via
RCU_INIT_POINTER(). It's problematic for some of the classifiers, because
this doesn't respect RCU grace period for them, and as a result, still
outstanding readers from tc_classify() will try to blindly dereference
a NULL tp->root.

The tp->root object is strictly private to the classifier implementation
and holds internal data the core such as tc_ctl_tfilter() doesn't know
about. Within some classifiers, such as cls_bpf, cls_basic, etc, tp->root
is only checked for NULL in ->get() callback, but nowhere else. This is
misleading and seemed to be copied from old classifier code that was not
cleaned up properly. For example, d3fa76ee6b ("[NET_SCHED]: cls_basic:
fix NULL pointer dereference") moved tp->root initialization into ->init()
routine, where before it was part of ->change(), so ->get() had to deal
with tp->root being NULL back then, so that was indeed a valid case, after
d3fa76ee6b, not really anymore. We used to set tp->root to NULL long
ago in ->destroy(), see 47a1a1d4be ("pkt_sched: remove unnecessary xchg()
in packet classifiers"); but the NULLifying was reintroduced with the
RCUification, but it's not correct for every classifier implementation.

In the cases that are fixed here with one exception of cls_cgroup, tp->root
object is allocated and initialized inside ->init() callback, which is always
performed at a point in time after we allocate a new tp, which means tp and
thus tp->root was not globally visible in the tp chain yet (see tc_ctl_tfilter()).
Also, on destruction tp->root is strictly kfree_rcu()'ed in ->destroy()
handler, same for the tp which is kfree_rcu()'ed right when we return
from ->destroy() in tcf_destroy(). This means, the head object's lifetime
for such classifiers is always tied to the tp lifetime. The RCU callback
invocation for the two kfree_rcu() could be out of order, but that's fine
since both are independent.

Dropping the RCU_INIT_POINTER(tp->root, NULL) for these classifiers here
means that 1) we don't need a useless NULL check in fast-path and, 2) that
outstanding readers of that tp in tc_classify() can still execute under
respect with RCU grace period as it is actually expected.

Things that haven't been touched here: cls_fw and cls_route. They each
handle tp->root being NULL in ->classify() path for historic reasons, so
their ->destroy() implementation can stay as is. If someone actually
cares, they could get cleaned up at some point to avoid the test in fast
path. cls_u32 doesn't set tp->root to NULL. For cls_rsvp, I just added a
!head should anyone actually be using/testing it, so it at least aligns with
cls_fw and cls_route. For cls_flower we additionally need to defer rhashtable
destruction (to a sleepable context) after RCU grace period as concurrent
readers might still access it. (Note that in this case we need to hold module
reference to keep work callback address intact, since we only wait on module
unload for all call_rcu()s to finish.)

This fixes one race to bring RCU grace period guarantees back. Next step
as worked on by Cong however is to fix 1e052be69d ("net_sched: destroy
proto tp when all filters are gone") to get the order of unlinking the tp
in tc_ctl_tfilter() for the RTM_DELTFILTER case right by moving
RCU_INIT_POINTER() before tcf_destroy() and let the notification for
removal be done through the prior ->delete() callback. Both are independant
issues. Once we have that right, we can then clean tp->root up for a number
of classifiers by not making them RCU pointers, which requires a new callback
(->uninit) that is triggered from tp's RCU callback, where we just kfree()
tp->root from there.

Fixes: 1f947bf151 ("net: sched: rcu'ify cls_bpf")
Fixes: 9888faefe1 ("net: sched: cls_basic use RCU")
Fixes: 70da9f0bf9 ("net: sched: cls_flow use RCU")
Fixes: 77b9900ef5 ("tc: introduce Flower classifier")
Fixes: bf3994d2ed ("net/sched: introduce Match-all classifier")
Fixes: 952313bd62 ("net: sched: cls_cgroup use RCU")
Reported-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Roi Dayan <roid@mellanox.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-11-28 10:47:35 -05:00

639 lines
15 KiB
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/*
* net/sched/cls_tcindex.c Packet classifier for skb->tc_index
*
* Written 1998,1999 by Werner Almesberger, EPFL ICA
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <net/act_api.h>
#include <net/netlink.h>
#include <net/pkt_cls.h>
/*
* Passing parameters to the root seems to be done more awkwardly than really
* necessary. At least, u32 doesn't seem to use such dirty hacks. To be
* verified. FIXME.
*/
#define PERFECT_HASH_THRESHOLD 64 /* use perfect hash if not bigger */
#define DEFAULT_HASH_SIZE 64 /* optimized for diffserv */
struct tcindex_filter_result {
struct tcf_exts exts;
struct tcf_result res;
struct rcu_head rcu;
};
struct tcindex_filter {
u16 key;
struct tcindex_filter_result result;
struct tcindex_filter __rcu *next;
struct rcu_head rcu;
};
struct tcindex_data {
struct tcindex_filter_result *perfect; /* perfect hash; NULL if none */
struct tcindex_filter __rcu **h; /* imperfect hash; */
struct tcf_proto *tp;
u16 mask; /* AND key with mask */
u32 shift; /* shift ANDed key to the right */
u32 hash; /* hash table size; 0 if undefined */
u32 alloc_hash; /* allocated size */
u32 fall_through; /* 0: only classify if explicit match */
struct rcu_head rcu;
};
static inline int tcindex_filter_is_set(struct tcindex_filter_result *r)
{
return tcf_exts_is_predicative(&r->exts) || r->res.classid;
}
static struct tcindex_filter_result *tcindex_lookup(struct tcindex_data *p,
u16 key)
{
if (p->perfect) {
struct tcindex_filter_result *f = p->perfect + key;
return tcindex_filter_is_set(f) ? f : NULL;
} else if (p->h) {
struct tcindex_filter __rcu **fp;
struct tcindex_filter *f;
fp = &p->h[key % p->hash];
for (f = rcu_dereference_bh_rtnl(*fp);
f;
fp = &f->next, f = rcu_dereference_bh_rtnl(*fp))
if (f->key == key)
return &f->result;
}
return NULL;
}
static int tcindex_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct tcf_result *res)
{
struct tcindex_data *p = rcu_dereference_bh(tp->root);
struct tcindex_filter_result *f;
int key = (skb->tc_index & p->mask) >> p->shift;
pr_debug("tcindex_classify(skb %p,tp %p,res %p),p %p\n",
skb, tp, res, p);
f = tcindex_lookup(p, key);
if (!f) {
if (!p->fall_through)
return -1;
res->classid = TC_H_MAKE(TC_H_MAJ(tp->q->handle), key);
res->class = 0;
pr_debug("alg 0x%x\n", res->classid);
return 0;
}
*res = f->res;
pr_debug("map 0x%x\n", res->classid);
return tcf_exts_exec(skb, &f->exts, res);
}
static unsigned long tcindex_get(struct tcf_proto *tp, u32 handle)
{
struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r;
pr_debug("tcindex_get(tp %p,handle 0x%08x)\n", tp, handle);
if (p->perfect && handle >= p->alloc_hash)
return 0;
r = tcindex_lookup(p, handle);
return r && tcindex_filter_is_set(r) ? (unsigned long) r : 0UL;
}
static int tcindex_init(struct tcf_proto *tp)
{
struct tcindex_data *p;
pr_debug("tcindex_init(tp %p)\n", tp);
p = kzalloc(sizeof(struct tcindex_data), GFP_KERNEL);
if (!p)
return -ENOMEM;
p->mask = 0xffff;
p->hash = DEFAULT_HASH_SIZE;
p->fall_through = 1;
rcu_assign_pointer(tp->root, p);
return 0;
}
static void tcindex_destroy_rexts(struct rcu_head *head)
{
struct tcindex_filter_result *r;
r = container_of(head, struct tcindex_filter_result, rcu);
tcf_exts_destroy(&r->exts);
}
static void tcindex_destroy_fexts(struct rcu_head *head)
{
struct tcindex_filter *f = container_of(head, struct tcindex_filter,
rcu);
tcf_exts_destroy(&f->result.exts);
kfree(f);
}
static int tcindex_delete(struct tcf_proto *tp, unsigned long arg)
{
struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r = (struct tcindex_filter_result *) arg;
struct tcindex_filter __rcu **walk;
struct tcindex_filter *f = NULL;
pr_debug("tcindex_delete(tp %p,arg 0x%lx),p %p\n", tp, arg, p);
if (p->perfect) {
if (!r->res.class)
return -ENOENT;
} else {
int i;
for (i = 0; i < p->hash; i++) {
walk = p->h + i;
for (f = rtnl_dereference(*walk); f;
walk = &f->next, f = rtnl_dereference(*walk)) {
if (&f->result == r)
goto found;
}
}
return -ENOENT;
found:
rcu_assign_pointer(*walk, rtnl_dereference(f->next));
}
tcf_unbind_filter(tp, &r->res);
/* all classifiers are required to call tcf_exts_destroy() after rcu
* grace period, since converted-to-rcu actions are relying on that
* in cleanup() callback
*/
if (f)
call_rcu(&f->rcu, tcindex_destroy_fexts);
else
call_rcu(&r->rcu, tcindex_destroy_rexts);
return 0;
}
static int tcindex_destroy_element(struct tcf_proto *tp,
unsigned long arg,
struct tcf_walker *walker)
{
return tcindex_delete(tp, arg);
}
static void __tcindex_destroy(struct rcu_head *head)
{
struct tcindex_data *p = container_of(head, struct tcindex_data, rcu);
kfree(p->perfect);
kfree(p->h);
kfree(p);
}
static inline int
valid_perfect_hash(struct tcindex_data *p)
{
return p->hash > (p->mask >> p->shift);
}
static const struct nla_policy tcindex_policy[TCA_TCINDEX_MAX + 1] = {
[TCA_TCINDEX_HASH] = { .type = NLA_U32 },
[TCA_TCINDEX_MASK] = { .type = NLA_U16 },
[TCA_TCINDEX_SHIFT] = { .type = NLA_U32 },
[TCA_TCINDEX_FALL_THROUGH] = { .type = NLA_U32 },
[TCA_TCINDEX_CLASSID] = { .type = NLA_U32 },
};
static int tcindex_filter_result_init(struct tcindex_filter_result *r)
{
memset(r, 0, sizeof(*r));
return tcf_exts_init(&r->exts, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
}
static void __tcindex_partial_destroy(struct rcu_head *head)
{
struct tcindex_data *p = container_of(head, struct tcindex_data, rcu);
kfree(p->perfect);
kfree(p);
}
static void tcindex_free_perfect_hash(struct tcindex_data *cp)
{
int i;
for (i = 0; i < cp->hash; i++)
tcf_exts_destroy(&cp->perfect[i].exts);
kfree(cp->perfect);
}
static int tcindex_alloc_perfect_hash(struct tcindex_data *cp)
{
int i, err = 0;
cp->perfect = kcalloc(cp->hash, sizeof(struct tcindex_filter_result),
GFP_KERNEL);
if (!cp->perfect)
return -ENOMEM;
for (i = 0; i < cp->hash; i++) {
err = tcf_exts_init(&cp->perfect[i].exts,
TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
if (err < 0)
goto errout;
}
return 0;
errout:
tcindex_free_perfect_hash(cp);
return err;
}
static int
tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base,
u32 handle, struct tcindex_data *p,
struct tcindex_filter_result *r, struct nlattr **tb,
struct nlattr *est, bool ovr)
{
struct tcindex_filter_result new_filter_result, *old_r = r;
struct tcindex_filter_result cr;
struct tcindex_data *cp = NULL, *oldp;
struct tcindex_filter *f = NULL; /* make gcc behave */
int err, balloc = 0;
struct tcf_exts e;
err = tcf_exts_init(&e, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
if (err < 0)
return err;
err = tcf_exts_validate(net, tp, tb, est, &e, ovr);
if (err < 0)
goto errout;
err = -ENOMEM;
/* tcindex_data attributes must look atomic to classifier/lookup so
* allocate new tcindex data and RCU assign it onto root. Keeping
* perfect hash and hash pointers from old data.
*/
cp = kzalloc(sizeof(*cp), GFP_KERNEL);
if (!cp)
goto errout;
cp->mask = p->mask;
cp->shift = p->shift;
cp->hash = p->hash;
cp->alloc_hash = p->alloc_hash;
cp->fall_through = p->fall_through;
cp->tp = tp;
if (p->perfect) {
int i;
if (tcindex_alloc_perfect_hash(cp) < 0)
goto errout;
for (i = 0; i < cp->hash; i++)
cp->perfect[i].res = p->perfect[i].res;
balloc = 1;
}
cp->h = p->h;
err = tcindex_filter_result_init(&new_filter_result);
if (err < 0)
goto errout1;
err = tcindex_filter_result_init(&cr);
if (err < 0)
goto errout1;
if (old_r)
cr.res = r->res;
if (tb[TCA_TCINDEX_HASH])
cp->hash = nla_get_u32(tb[TCA_TCINDEX_HASH]);
if (tb[TCA_TCINDEX_MASK])
cp->mask = nla_get_u16(tb[TCA_TCINDEX_MASK]);
if (tb[TCA_TCINDEX_SHIFT])
cp->shift = nla_get_u32(tb[TCA_TCINDEX_SHIFT]);
err = -EBUSY;
/* Hash already allocated, make sure that we still meet the
* requirements for the allocated hash.
*/
if (cp->perfect) {
if (!valid_perfect_hash(cp) ||
cp->hash > cp->alloc_hash)
goto errout_alloc;
} else if (cp->h && cp->hash != cp->alloc_hash) {
goto errout_alloc;
}
err = -EINVAL;
if (tb[TCA_TCINDEX_FALL_THROUGH])
cp->fall_through = nla_get_u32(tb[TCA_TCINDEX_FALL_THROUGH]);
if (!cp->hash) {
/* Hash not specified, use perfect hash if the upper limit
* of the hashing index is below the threshold.
*/
if ((cp->mask >> cp->shift) < PERFECT_HASH_THRESHOLD)
cp->hash = (cp->mask >> cp->shift) + 1;
else
cp->hash = DEFAULT_HASH_SIZE;
}
if (!cp->perfect && !cp->h)
cp->alloc_hash = cp->hash;
/* Note: this could be as restrictive as if (handle & ~(mask >> shift))
* but then, we'd fail handles that may become valid after some future
* mask change. While this is extremely unlikely to ever matter,
* the check below is safer (and also more backwards-compatible).
*/
if (cp->perfect || valid_perfect_hash(cp))
if (handle >= cp->alloc_hash)
goto errout_alloc;
err = -ENOMEM;
if (!cp->perfect && !cp->h) {
if (valid_perfect_hash(cp)) {
if (tcindex_alloc_perfect_hash(cp) < 0)
goto errout_alloc;
balloc = 1;
} else {
struct tcindex_filter __rcu **hash;
hash = kcalloc(cp->hash,
sizeof(struct tcindex_filter *),
GFP_KERNEL);
if (!hash)
goto errout_alloc;
cp->h = hash;
balloc = 2;
}
}
if (cp->perfect)
r = cp->perfect + handle;
else
r = tcindex_lookup(cp, handle) ? : &new_filter_result;
if (r == &new_filter_result) {
f = kzalloc(sizeof(*f), GFP_KERNEL);
if (!f)
goto errout_alloc;
f->key = handle;
f->next = NULL;
err = tcindex_filter_result_init(&f->result);
if (err < 0) {
kfree(f);
goto errout_alloc;
}
}
if (tb[TCA_TCINDEX_CLASSID]) {
cr.res.classid = nla_get_u32(tb[TCA_TCINDEX_CLASSID]);
tcf_bind_filter(tp, &cr.res, base);
}
if (old_r)
tcf_exts_change(tp, &r->exts, &e);
else
tcf_exts_change(tp, &cr.exts, &e);
if (old_r && old_r != r) {
err = tcindex_filter_result_init(old_r);
if (err < 0) {
kfree(f);
goto errout_alloc;
}
}
oldp = p;
r->res = cr.res;
rcu_assign_pointer(tp->root, cp);
if (r == &new_filter_result) {
struct tcindex_filter *nfp;
struct tcindex_filter __rcu **fp;
tcf_exts_change(tp, &f->result.exts, &r->exts);
fp = cp->h + (handle % cp->hash);
for (nfp = rtnl_dereference(*fp);
nfp;
fp = &nfp->next, nfp = rtnl_dereference(*fp))
; /* nothing */
rcu_assign_pointer(*fp, f);
}
if (oldp)
call_rcu(&oldp->rcu, __tcindex_partial_destroy);
return 0;
errout_alloc:
if (balloc == 1)
tcindex_free_perfect_hash(cp);
else if (balloc == 2)
kfree(cp->h);
errout1:
tcf_exts_destroy(&cr.exts);
tcf_exts_destroy(&new_filter_result.exts);
errout:
kfree(cp);
tcf_exts_destroy(&e);
return err;
}
static int
tcindex_change(struct net *net, struct sk_buff *in_skb,
struct tcf_proto *tp, unsigned long base, u32 handle,
struct nlattr **tca, unsigned long *arg, bool ovr)
{
struct nlattr *opt = tca[TCA_OPTIONS];
struct nlattr *tb[TCA_TCINDEX_MAX + 1];
struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r = (struct tcindex_filter_result *) *arg;
int err;
pr_debug("tcindex_change(tp %p,handle 0x%08x,tca %p,arg %p),opt %p,"
"p %p,r %p,*arg 0x%lx\n",
tp, handle, tca, arg, opt, p, r, arg ? *arg : 0L);
if (!opt)
return 0;
err = nla_parse_nested(tb, TCA_TCINDEX_MAX, opt, tcindex_policy);
if (err < 0)
return err;
return tcindex_set_parms(net, tp, base, handle, p, r, tb,
tca[TCA_RATE], ovr);
}
static void tcindex_walk(struct tcf_proto *tp, struct tcf_walker *walker)
{
struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter *f, *next;
int i;
pr_debug("tcindex_walk(tp %p,walker %p),p %p\n", tp, walker, p);
if (p->perfect) {
for (i = 0; i < p->hash; i++) {
if (!p->perfect[i].res.class)
continue;
if (walker->count >= walker->skip) {
if (walker->fn(tp,
(unsigned long) (p->perfect+i), walker)
< 0) {
walker->stop = 1;
return;
}
}
walker->count++;
}
}
if (!p->h)
return;
for (i = 0; i < p->hash; i++) {
for (f = rtnl_dereference(p->h[i]); f; f = next) {
next = rtnl_dereference(f->next);
if (walker->count >= walker->skip) {
if (walker->fn(tp, (unsigned long) &f->result,
walker) < 0) {
walker->stop = 1;
return;
}
}
walker->count++;
}
}
}
static bool tcindex_destroy(struct tcf_proto *tp, bool force)
{
struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcf_walker walker;
if (!force)
return false;
pr_debug("tcindex_destroy(tp %p),p %p\n", tp, p);
walker.count = 0;
walker.skip = 0;
walker.fn = tcindex_destroy_element;
tcindex_walk(tp, &walker);
call_rcu(&p->rcu, __tcindex_destroy);
return true;
}
static int tcindex_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
struct sk_buff *skb, struct tcmsg *t)
{
struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r = (struct tcindex_filter_result *) fh;
struct nlattr *nest;
pr_debug("tcindex_dump(tp %p,fh 0x%lx,skb %p,t %p),p %p,r %p\n",
tp, fh, skb, t, p, r);
pr_debug("p->perfect %p p->h %p\n", p->perfect, p->h);
nest = nla_nest_start(skb, TCA_OPTIONS);
if (nest == NULL)
goto nla_put_failure;
if (!fh) {
t->tcm_handle = ~0; /* whatever ... */
if (nla_put_u32(skb, TCA_TCINDEX_HASH, p->hash) ||
nla_put_u16(skb, TCA_TCINDEX_MASK, p->mask) ||
nla_put_u32(skb, TCA_TCINDEX_SHIFT, p->shift) ||
nla_put_u32(skb, TCA_TCINDEX_FALL_THROUGH, p->fall_through))
goto nla_put_failure;
nla_nest_end(skb, nest);
} else {
if (p->perfect) {
t->tcm_handle = r - p->perfect;
} else {
struct tcindex_filter *f;
struct tcindex_filter __rcu **fp;
int i;
t->tcm_handle = 0;
for (i = 0; !t->tcm_handle && i < p->hash; i++) {
fp = &p->h[i];
for (f = rtnl_dereference(*fp);
!t->tcm_handle && f;
fp = &f->next, f = rtnl_dereference(*fp)) {
if (&f->result == r)
t->tcm_handle = f->key;
}
}
}
pr_debug("handle = %d\n", t->tcm_handle);
if (r->res.class &&
nla_put_u32(skb, TCA_TCINDEX_CLASSID, r->res.classid))
goto nla_put_failure;
if (tcf_exts_dump(skb, &r->exts) < 0)
goto nla_put_failure;
nla_nest_end(skb, nest);
if (tcf_exts_dump_stats(skb, &r->exts) < 0)
goto nla_put_failure;
}
return skb->len;
nla_put_failure:
nla_nest_cancel(skb, nest);
return -1;
}
static struct tcf_proto_ops cls_tcindex_ops __read_mostly = {
.kind = "tcindex",
.classify = tcindex_classify,
.init = tcindex_init,
.destroy = tcindex_destroy,
.get = tcindex_get,
.change = tcindex_change,
.delete = tcindex_delete,
.walk = tcindex_walk,
.dump = tcindex_dump,
.owner = THIS_MODULE,
};
static int __init init_tcindex(void)
{
return register_tcf_proto_ops(&cls_tcindex_ops);
}
static void __exit exit_tcindex(void)
{
unregister_tcf_proto_ops(&cls_tcindex_ops);
}
module_init(init_tcindex)
module_exit(exit_tcindex)
MODULE_LICENSE("GPL");
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