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

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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: 9b0d4446b5 ("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>
This commit is contained in:
Pedro Tammela 2023-02-09 11:37:39 -03:00 committed by Jakub Kicinski
parent a1221703a0
commit ee059170b1
1 changed files with 30 additions and 4 deletions
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34
net/sched/cls_tcindex.c
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@ -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;