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Commit 18cdb37e authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
Browse files

net: sched: do not use tcf_proto 'tp' argument from call_rcu 



Using the tcf_proto pointer 'tp' from inside the classifiers callback
is not valid because it may have been cleaned up by another call_rcu
occuring on another CPU.

'tp' is currently being used by tcf_unbind_filter() in this patch we
move instances of tcf_unbind_filter outside of the call_rcu() context.
This is safe to do because any running schedulers will either read the
valid class field or it will be zeroed.

And all schedulers today when the class is 0 do a lookup using the
same call used by the tcf_exts_bind(). So even if we have a running
classifier hit the null class pointer it will do a lookup and get
to the same result. This is particularly fragile at the moment because
the only way to verify this is to audit the schedulers call sites.

Reported-by: default avatarCong Wang <xiyou.wangconf@gmail.com>
Signed-off-by: default avatarJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: default avatarCong Wang <cwang@twopensource.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 13990f81

net/sched/cls_basic.c

+3 −2
Original line number Diff line number Diff line
@@ -91,9 +91,7 @@ static int basic_init(struct tcf_proto *tp) 
static void basic_delete_filter(struct rcu_head *head)

{

	struct basic_filter *f = container_of(head, struct basic_filter, rcu);

	struct tcf_proto *tp = f->tp;



	tcf_unbind_filter(tp, &f->res);

	tcf_exts_destroy(&f->exts);

	tcf_em_tree_destroy(&f->ematches);

	kfree(f);
@@ -106,6 +104,7 @@ static void basic_destroy(struct tcf_proto *tp) 


	list_for_each_entry_safe(f, n, &head->flist, link) {

		list_del_rcu(&f->link);

		tcf_unbind_filter(tp, &f->res);

		call_rcu(&f->rcu, basic_delete_filter);

	}

	RCU_INIT_POINTER(tp->root, NULL);
@@ -120,6 +119,7 @@ static int basic_delete(struct tcf_proto *tp, unsigned long arg) 
	list_for_each_entry(t, &head->flist, link)

		if (t == f) {

			list_del_rcu(&t->link);

			tcf_unbind_filter(tp, &t->res);

			call_rcu(&t->rcu, basic_delete_filter);

			return 0;

		}
@@ -222,6 +222,7 @@ static int basic_change(struct net *net, struct sk_buff *in_skb, 


	if (fold) {

		list_replace_rcu(&fold->link, &fnew->link);

		tcf_unbind_filter(tp, &fold->res);

		call_rcu(&fold->rcu, basic_delete_filter);

	} else {

		list_add_rcu(&fnew->link, &head->flist);

net/sched/cls_bpf.c

+3 −1
Original line number Diff line number Diff line
@@ -92,7 +92,6 @@ static int cls_bpf_init(struct tcf_proto *tp) 


static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)

{

	tcf_unbind_filter(tp, &prog->res);

	tcf_exts_destroy(&prog->exts);



	bpf_prog_destroy(prog->filter);
@@ -116,6 +115,7 @@ static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg) 
	list_for_each_entry(prog, &head->plist, link) {

		if (prog == todel) {

			list_del_rcu(&prog->link);

			tcf_unbind_filter(tp, &prog->res);

			call_rcu(&prog->rcu, __cls_bpf_delete_prog);

			return 0;

		}
@@ -131,6 +131,7 @@ static void cls_bpf_destroy(struct tcf_proto *tp) 


	list_for_each_entry_safe(prog, tmp, &head->plist, link) {

		list_del_rcu(&prog->link);

		tcf_unbind_filter(tp, &prog->res);

		call_rcu(&prog->rcu, __cls_bpf_delete_prog);

	}
@@ -282,6 +283,7 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb, 


	if (oldprog) {

		list_replace_rcu(&prog->link, &oldprog->link);

		tcf_unbind_filter(tp, &oldprog->res);

		call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);

	} else {

		list_add_rcu(&prog->link, &head->plist);

net/sched/cls_fw.c

+3 −2
Original line number Diff line number Diff line
@@ -123,9 +123,7 @@ static int fw_init(struct tcf_proto *tp) 
static void fw_delete_filter(struct rcu_head *head)

{

	struct fw_filter *f = container_of(head, struct fw_filter, rcu);

	struct tcf_proto *tp = f->tp;



	tcf_unbind_filter(tp, &f->res);

	tcf_exts_destroy(&f->exts);

	kfree(f);

}
@@ -143,6 +141,7 @@ static void fw_destroy(struct tcf_proto *tp) 
		while ((f = rtnl_dereference(head->ht[h])) != NULL) {

			RCU_INIT_POINTER(head->ht[h],

					 rtnl_dereference(f->next));

			tcf_unbind_filter(tp, &f->res);

			call_rcu(&f->rcu, fw_delete_filter);

		}

	}
@@ -166,6 +165,7 @@ static int fw_delete(struct tcf_proto *tp, unsigned long arg) 
	     fp = &pfp->next, pfp = rtnl_dereference(*fp)) {

		if (pfp == f) {

			RCU_INIT_POINTER(*fp, rtnl_dereference(f->next));

			tcf_unbind_filter(tp, &f->res);

			call_rcu(&f->rcu, fw_delete_filter);

			return 0;

		}
@@ -280,6 +280,7 @@ static int fw_change(struct net *net, struct sk_buff *in_skb, 


		RCU_INIT_POINTER(fnew->next, rtnl_dereference(pfp->next));

		rcu_assign_pointer(*fp, fnew);

		tcf_unbind_filter(tp, &f->res);

		call_rcu(&f->rcu, fw_delete_filter);



		*arg = (unsigned long)fnew;

net/sched/cls_route.c

+5 −3
Original line number Diff line number Diff line
@@ -269,9 +269,7 @@ static void 
route4_delete_filter(struct rcu_head *head)

{

	struct route4_filter *f = container_of(head, struct route4_filter, rcu);

	struct tcf_proto *tp = f->tp;



	tcf_unbind_filter(tp, &f->res);

	tcf_exts_destroy(&f->exts);

	kfree(f);

}
@@ -297,6 +295,7 @@ static void route4_destroy(struct tcf_proto *tp) 


					next = rtnl_dereference(f->next);

					RCU_INIT_POINTER(b->ht[h2], next);

					tcf_unbind_filter(tp, &f->res);

					call_rcu(&f->rcu, route4_delete_filter);

				}

			}
@@ -338,6 +337,7 @@ static int route4_delete(struct tcf_proto *tp, unsigned long arg) 
			route4_reset_fastmap(head);



			/* Delete it */

			tcf_unbind_filter(tp, &f->res);

			call_rcu(&f->rcu, route4_delete_filter);



			/* Strip RTNL protected tree */
@@ -545,8 +545,10 @@ static int route4_change(struct net *net, struct sk_buff *in_skb, 


	route4_reset_fastmap(head);

	*arg = (unsigned long)f;

	if (fold)

	if (fold) {

		tcf_unbind_filter(tp, &fold->res);

		call_rcu(&fold->rcu, route4_delete_filter);

	}

	return 0;



errout: