From: Pedro Tammela pctammela@mojatatu.com
commit ee059170b1f7e94e55fa6cadee544e176a6e59c2 upstream.
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 Link: https://lore.kernel.org/r/20230209143739.279867-1-pctammela@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/cls_tcindex.c | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-)
--- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -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> @@ -338,6 +339,7 @@ tcindex_set_parms(struct net *net, struc 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) @@ -455,10 +457,13 @@ tcindex_set_parms(struct net *net, struc } }
- 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); @@ -484,7 +489,28 @@ tcindex_set_parms(struct net *net, struc
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;