Commit ee059170 authored by Pedro Tammela's avatar Pedro Tammela Committed by Jakub Kicinski
Browse files

net/sched: tcindex: update imperfect hash filters respecting rcu 



The imperfect hash area can be updated while packets are traversing,
which will cause a use-after-free when 'tcf_exts_exec()' is called
with the destroyed tcf_ext.

CPU 0:               CPU 1:
tcindex_set_parms    tcindex_classify
tcindex_lookup
                     tcindex_lookup
tcf_exts_change
                     tcf_exts_exec [UAF]

Stop operating on the shared area directly, by using a local copy,
and update the filter with 'rcu_replace_pointer()'. Delete the old
filter version only after a rcu grace period elapsed.

Fixes: 9b0d4446 ("net: sched: avoid atomic swap in tcf_exts_change")
Reported-by: default avatarvalis <sec@valis.email>
Suggested-by: default avatarvalis <sec@valis.email>
Signed-off-by: default avatarJamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: default avatarPedro Tammela <pctammela@mojatatu.com>
Link: https://lore.kernel.org/r/20230209143739.279867-1-pctammela@mojatatu.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a1221703

net/sched/cls_tcindex.c

+30 −4
Original line number Original line Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/errno.h>

#include <linux/errno.h>

#include <linux/slab.h>

#include <linux/slab.h>

#include <linux/refcount.h>

#include <linux/refcount.h>

#include <linux/rcupdate.h>

#include <net/act_api.h>

#include <net/act_api.h>

#include <net/netlink.h>

#include <net/netlink.h>

#include <net/pkt_cls.h>

#include <net/pkt_cls.h>
@@ -339,6 +340,7 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
	struct tcf_result cr = {};

	struct tcf_result cr = {};

	int err, balloc = 0;

	int err, balloc = 0;

	struct tcf_exts e;

	struct tcf_exts e;

	bool update_h = false;





	err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);

	err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);

	if (err < 0)

	if (err < 0)
@@ -456,10 +458,13 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 
		}

		}

	}

	}





	if (cp->perfect)

	if (cp->perfect) {

		r = cp->perfect + handle;

		r = cp->perfect + handle;

	else

	} else {

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

		/* imperfect area is updated in-place using rcu */

		update_h = !!tcindex_lookup(cp, handle);

		r = &new_filter_result;

	}





	if (r == &new_filter_result) {

	if (r == &new_filter_result) {

		f = kzalloc(sizeof(*f), GFP_KERNEL);

		f = kzalloc(sizeof(*f), GFP_KERNEL);
@@ -485,7 +490,28 @@ tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base, 




	rcu_assign_pointer(tp->root, cp);

	rcu_assign_pointer(tp->root, cp);





	if (r == &new_filter_result) {

	if (update_h) {

		struct tcindex_filter __rcu **fp;

		struct tcindex_filter *cf;



		f->result.res = r->res;

		tcf_exts_change(&f->result.exts, &r->exts);



		/* imperfect area bucket */

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



		/* lookup the filter, guaranteed to exist */

		for (cf = rcu_dereference_bh_rtnl(*fp); cf;

		     fp = &cf->next, cf = rcu_dereference_bh_rtnl(*fp))

			if (cf->key == handle)

				break;



		f->next = cf->next;



		cf = rcu_replace_pointer(*fp, f, 1);

		tcf_exts_get_net(&cf->result.exts);

		tcf_queue_work(&cf->rwork, tcindex_destroy_fexts_work);

	} else if (r == &new_filter_result) {

		struct tcindex_filter *nfp;

		struct tcindex_filter *nfp;

		struct tcindex_filter __rcu **fp;

		struct tcindex_filter __rcu **fp;