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Commit 331b7292 authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
Browse files

net: sched: RCU cls_tcindex 



Make cls_tcindex RCU safe.

This patch addds a new RCU routine rcu_dereference_bh_rtnl() to check
caller either holds the rcu read lock or RTNL. This is needed to
handle the case where tcindex_lookup() is being called in both cases.

Signed-off-by: default avatarJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1109c005

include/linux/rtnetlink.h

+10 −0
Original line number Diff line number Diff line
@@ -46,6 +46,16 @@ static inline int lockdep_rtnl_is_held(void) 
#define rcu_dereference_rtnl(p)					\

	rcu_dereference_check(p, lockdep_rtnl_is_held())



/**

 * rcu_dereference_bh_rtnl - rcu_dereference_bh with debug checking

 * @p: The pointer to read, prior to dereference

 *

 * Do an rcu_dereference_bh(p), but check caller either holds rcu_read_lock_bh()

 * or RTNL. Note : Please prefer rtnl_dereference() or rcu_dereference_bh()

 */

#define rcu_dereference_bh_rtnl(p)				\

	rcu_dereference_bh_check(p, lockdep_rtnl_is_held())



/**

 * rtnl_dereference - fetch RCU pointer when updates are prevented by RTNL

 * @p: The pointer to read, prior to dereferencing

net/sched/cls_tcindex.c

+154 −94
Original line number Diff line number Diff line
@@ -32,19 +32,21 @@ struct tcindex_filter_result { 
struct tcindex_filter {

	u16 key;

	struct tcindex_filter_result result;

	struct tcindex_filter *next;

	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 **h; /* imperfect hash; only used if !perfect;

				      NULL if unused */

	struct tcindex_filter __rcu **h; /* imperfect hash; */

	struct tcf_proto *tp;

	u16 mask;		/* AND key with mask */

	int shift;		/* shift ANDed key to the right */

	int hash;		/* hash table size; 0 if undefined */

	int alloc_hash;		/* allocated size */

	int fall_through;	/* 0: only classify if explicit match */

	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
@@ -56,13 +58,18 @@ tcindex_filter_is_set(struct tcindex_filter_result *r) 
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;



	if (p->perfect)

		return tcindex_filter_is_set(p->perfect + key) ?

			p->perfect + key : NULL;

	else if (p->h) {

		for (f = p->h[key % p->hash]; f; f = f->next)

		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;

	}
@@ -74,7 +81,7 @@ tcindex_lookup(struct tcindex_data *p, u16 key) 
static int tcindex_classify(struct sk_buff *skb, const struct tcf_proto *tp,

			    struct tcf_result *res)

{

	struct tcindex_data *p = tp->root;

	struct tcindex_data *p = rcu_dereference(tp->root);

	struct tcindex_filter_result *f;

	int key = (skb->tc_index & p->mask) >> p->shift;
@@ -99,7 +106,7 @@ static int tcindex_classify(struct sk_buff *skb, const struct tcf_proto *tp, 


static unsigned long tcindex_get(struct tcf_proto *tp, u32 handle)

{

	struct tcindex_data *p = tp->root;

	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);
@@ -129,49 +136,59 @@ static int tcindex_init(struct tcf_proto *tp) 
	p->hash = DEFAULT_HASH_SIZE;

	p->fall_through = 1;



	tp->root = p;

	rcu_assign_pointer(tp->root, p);

	return 0;

}





static int

__tcindex_delete(struct tcf_proto *tp, unsigned long arg, int lock)

tcindex_delete(struct tcf_proto *tp, unsigned long arg)

{

	struct tcindex_data *p = tp->root;

	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,f %p\n", tp, arg, p, f);

	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;

		struct tcindex_filter **walk = NULL;



		for (i = 0; i < p->hash; i++)

			for (walk = p->h+i; *walk; walk = &(*walk)->next)

				if (&(*walk)->result == r)

		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:

		f = *walk;

		if (lock)

			tcf_tree_lock(tp);

		*walk = f->next;

		if (lock)

			tcf_tree_unlock(tp);

		rcu_assign_pointer(*walk, rtnl_dereference(f->next));

	}

	tcf_unbind_filter(tp, &r->res);

	tcf_exts_destroy(tp, &r->exts);

	kfree(f);

	if (f)

		kfree_rcu(f, rcu);

	return 0;

}



static int tcindex_delete(struct tcf_proto *tp, unsigned long arg)

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)

{

	return __tcindex_delete(tp, arg, 1);

	struct tcindex_data *p = container_of(head, struct tcindex_data, rcu);



	kfree(p->perfect);

	kfree(p->h);

	kfree(p);

}



static inline int
@@ -194,6 +211,14 @@ static void tcindex_filter_result_init(struct tcindex_filter_result *r) 
	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 int

tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base,

		  u32 handle, struct tcindex_data *p,
@@ -203,7 +228,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
	int err, balloc = 0;

	struct tcindex_filter_result new_filter_result, *old_r = r;

	struct tcindex_filter_result cr;

	struct tcindex_data cp;

	struct tcindex_data *cp, *oldp;

	struct tcindex_filter *f = NULL; /* make gcc behave */

	struct tcf_exts e;
@@ -212,84 +237,118 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
	if (err < 0)

		return err;



	memcpy(&cp, p, sizeof(cp));

	tcindex_filter_result_init(&new_filter_result);

	/* 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)

		return -ENOMEM;



	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) {

		cp->perfect = kmemdup(p->perfect,

				      sizeof(*r) * cp->hash, GFP_KERNEL);

		if (!cp->perfect)

			goto errout;

	}

	cp->h = p->h;



	memset(&new_filter_result, 0, sizeof(new_filter_result));

	tcf_exts_init(&new_filter_result.exts,

		      TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);



	tcindex_filter_result_init(&cr);

	if (old_r)

		cr.res = r->res;



	if (tb[TCA_TCINDEX_HASH])

		cp.hash = nla_get_u32(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]);

		cp->mask = nla_get_u16(tb[TCA_TCINDEX_MASK]);



	if (tb[TCA_TCINDEX_SHIFT])

		cp.shift = nla_get_u32(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)

	if (cp->perfect) {

		if (!valid_perfect_hash(cp) ||

		    cp->hash > cp->alloc_hash)

			goto errout;

	} else if (cp.h && cp.hash != cp.alloc_hash)

	} else if (cp->h && cp->hash != cp->alloc_hash) {

		goto errout;

	}



	err = -EINVAL;

	if (tb[TCA_TCINDEX_FALL_THROUGH])

		cp.fall_through = nla_get_u32(tb[TCA_TCINDEX_FALL_THROUGH]);

		cp->fall_through = nla_get_u32(tb[TCA_TCINDEX_FALL_THROUGH]);



	if (!cp.hash) {

	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;

		if ((cp->mask >> cp->shift) < PERFECT_HASH_THRESHOLD)

			cp->hash = (cp->mask >> cp->shift) + 1;

		else

			cp.hash = DEFAULT_HASH_SIZE;

			cp->hash = DEFAULT_HASH_SIZE;

	}



	if (!cp.perfect && !cp.h)

		cp.alloc_hash = cp.hash;

	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)

	if (cp->perfect || valid_perfect_hash(cp))

		if (handle >= cp->alloc_hash)

			goto errout;





	err = -ENOMEM;

	if (!cp.perfect && !cp.h) {

		if (valid_perfect_hash(&cp)) {

	if (!cp->perfect && !cp->h) {

		if (valid_perfect_hash(cp)) {

			int i;



			cp.perfect = kcalloc(cp.hash, sizeof(*r), GFP_KERNEL);

			if (!cp.perfect)

			cp->perfect = kcalloc(cp->hash, sizeof(*r), GFP_KERNEL);

			if (!cp->perfect)

				goto errout;

			for (i = 0; i < cp.hash; i++)

				tcf_exts_init(&cp.perfect[i].exts, TCA_TCINDEX_ACT,

			for (i = 0; i < cp->hash; i++)

				tcf_exts_init(&cp->perfect[i].exts,

					      TCA_TCINDEX_ACT,

					      TCA_TCINDEX_POLICE);

			balloc = 1;

		} else {

			cp.h = kcalloc(cp.hash, sizeof(f), GFP_KERNEL);

			if (!cp.h)

			struct tcindex_filter __rcu **hash;



			hash = kcalloc(cp->hash,

				       sizeof(struct tcindex_filter *),

				       GFP_KERNEL);



			if (!hash)

				goto errout;



			cp->h = hash;

			balloc = 2;

		}

	}



	if (cp.perfect)

		r = cp.perfect + handle;

	if (cp->perfect)

		r = cp->perfect + handle;

	else

		r = tcindex_lookup(&cp, handle) ? : &new_filter_result;

		r = tcindex_lookup(cp, handle) ? : &new_filter_result;



	if (r == &new_filter_result) {

		f = kzalloc(sizeof(*f), GFP_KERNEL);
@@ -307,33 +366,41 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
	else

		tcf_exts_change(tp, &cr.exts, &e);



	tcf_tree_lock(tp);

	if (old_r && old_r != r)

		tcindex_filter_result_init(old_r);



	memcpy(p, &cp, sizeof(cp));

	oldp = p;

	r->res = cr.res;

	rcu_assign_pointer(tp->root, cp);



	if (r == &new_filter_result) {

		struct tcindex_filter **fp;

		struct tcindex_filter *nfp;

		struct tcindex_filter __rcu **fp;



		f->key = handle;

		f->result = new_filter_result;

		f->next = NULL;

		for (fp = p->h+(handle % p->hash); *fp; fp = &(*fp)->next)

			/* nothing */;

		*fp = f;



		fp = p->h + (handle % p->hash);

		for (nfp = rtnl_dereference(*fp);

		     nfp;

		     fp = &nfp->next, nfp = rtnl_dereference(*fp))

				; /* nothing */



		rcu_assign_pointer(*fp, f);

	}

	tcf_tree_unlock(tp);



	if (oldp)

		call_rcu(&oldp->rcu, __tcindex_partial_destroy);

	return 0;



errout_alloc:

	if (balloc == 1)

		kfree(cp.perfect);

		kfree(cp->perfect);

	else if (balloc == 2)

		kfree(cp.h);

		kfree(cp->h);

errout:

	kfree(cp);

	tcf_exts_destroy(tp, &e);

	return err;

}
@@ -345,7 +412,7 @@ tcindex_change(struct net *net, struct sk_buff *in_skb, 
{

	struct nlattr *opt = tca[TCA_OPTIONS];

	struct nlattr *tb[TCA_TCINDEX_MAX + 1];

	struct tcindex_data *p = tp->root;

	struct tcindex_data *p = rtnl_dereference(tp->root);

	struct tcindex_filter_result *r = (struct tcindex_filter_result *) *arg;

	int err;
@@ -364,10 +431,9 @@ tcindex_change(struct net *net, struct sk_buff *in_skb, 
				 tca[TCA_RATE], ovr);

}





static void tcindex_walk(struct tcf_proto *tp, struct tcf_walker *walker)

{

	struct tcindex_data *p = tp->root;

	struct tcindex_data *p = rtnl_dereference(tp->root);

	struct tcindex_filter *f, *next;

	int i;
@@ -390,8 +456,8 @@ static void tcindex_walk(struct tcf_proto *tp, struct tcf_walker *walker) 
	if (!p->h)

		return;

	for (i = 0; i < p->hash; i++) {

		for (f = p->h[i]; f; f = next) {

			next = f->next;

		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) {
@@ -404,17 +470,9 @@ static void tcindex_walk(struct tcf_proto *tp, struct tcf_walker *walker) 
	}

}





static int tcindex_destroy_element(struct tcf_proto *tp,

    unsigned long arg, struct tcf_walker *walker)

{

	return __tcindex_delete(tp, arg, 0);

}





static void tcindex_destroy(struct tcf_proto *tp)

{

	struct tcindex_data *p = tp->root;

	struct tcindex_data *p = rtnl_dereference(tp->root);

	struct tcf_walker walker;



	pr_debug("tcindex_destroy(tp %p),p %p\n", tp, p);
@@ -422,17 +480,16 @@ static void tcindex_destroy(struct tcf_proto *tp) 
	walker.skip = 0;

	walker.fn = tcindex_destroy_element;

	tcindex_walk(tp, &walker);

	kfree(p->perfect);

	kfree(p->h);

	kfree(p);

	tp->root = NULL;



	RCU_INIT_POINTER(tp->root, NULL);

	call_rcu(&p->rcu, __tcindex_destroy);

}





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 = tp->root;

	struct tcindex_data *p = rtnl_dereference(tp->root);

	struct tcindex_filter_result *r = (struct tcindex_filter_result *) fh;

	unsigned char *b = skb_tail_pointer(skb);

	struct nlattr *nest;
@@ -458,12 +515,15 @@ static int tcindex_dump(struct net *net, struct tcf_proto *tp, unsigned long fh, 
			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++) {

				for (f = p->h[i]; !t->tcm_handle && f;

				     f = f->next) {

				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;

				}