@@ -12,6 +12,7 @@
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/refcount.h>
+#include <linux/rcupdate.h>
#include <net/act_api.h>
#include <net/netlink.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 = {};
int err, balloc = 0;
struct tcf_exts e;
+ bool update_h = false;
err = tcf_exts_init(&e, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
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;
- else
- r = tcindex_lookup(cp, handle) ? : &new_filter_result;
+ } else {
+ /* imperfect area is updated in-place using rcu */
+ update_h = !!tcindex_lookup(cp, handle);
+ r = &new_filter_result;
+ }
if (r == &new_filter_result) {
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);
- 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 __rcu **fp;
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: 9b0d4446b569 ("net: sched: avoid atomic swap in tcf_exts_change") Reported-by: valis <sec@valis.email> Suggested-by: valis <sec@valis.email> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com> Signed-off-by: Pedro Tammela <pctammela@mojatatu.com> --- net/sched/cls_tcindex.c | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-)