[PATCH 5.4 06/43] act_ife: load meta modules before tcf_idr_check_alloc()

Greg Kroah-Hartman
2020-09-25T12:51:31Z

From: Cong Wang <xiyou.wangcong@gmail.com>

[ Upstream commit cc8e58f8325cdf14b9516b61c384cdfd02a4f408 ]

The following deadlock scenario is triggered by syzbot:

Thread A: Thread B:
tcf_idr_check_alloc()
...
populate_metalist()
rtnl_unlock()
rtnl_lock()
...
request_module() tcf_idr_check_alloc()
rtnl_lock()

At this point, thread A is waiting for thread B to release RTNL
lock, while thread B is waiting for thread A to commit the IDR
change with tcf_idr_insert() later.

Break this deadlock situation by preloading ife modules earlier,
before tcf_idr_check_alloc(), this is fine because we only need
to load modules we need potentially.

Reported-and-tested-by: syzbot+80e32b5d1f9923f8ace6@syzkaller.appspotmail.com
Fixes: 0190c1d452a9 ("net: sched: atomically check-allocate action")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Vlad Buslov <vladbu@mellanox.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/act_ife.c | 44 ++++++++++++++++++++++++++++++++++----------
1 file changed, 34 insertions(+), 10 deletions(-)

--- a/net/sched/act_ife.c
+++ b/net/sched/act_ife.c
@@ -436,6 +436,25 @@ static void tcf_ife_cleanup(struct tc_ac
kfree_rcu(p, rcu);
}

+static int load_metalist(struct nlattr **tb, bool rtnl_held)
+{
+ int i;
+
+ for (i = 1; i < max_metacnt; i++) {
+ if (tb[i]) {
+ void *val = nla_data(tb[i]);
+ int len = nla_len(tb[i]);
+ int rc;
+
+ rc = load_metaops_and_vet(i, val, len, rtnl_held);
+ if (rc != 0)
+ return rc;
+ }
+ }
+
+ return 0;
+}
+
static int populate_metalist(struct tcf_ife_info *ife, struct nlattr **tb,
bool exists, bool rtnl_held)
{
@@ -449,10 +468,6 @@ static int populate_metalist(struct tcf_
val = nla_data(tb[i]);
len = nla_len(tb[i]);

- rc = load_metaops_and_vet(i, val, len, rtnl_held);
- if (rc != 0)
- return rc;
-
rc = add_metainfo(ife, i, val, len, exists);
if (rc)
return rc;
@@ -508,6 +523,21 @@ static int tcf_ife_init(struct net *net,
if (!p)
return -ENOMEM;

+ if (tb[TCA_IFE_METALST]) {
+ err = nla_parse_nested_deprecated(tb2, IFE_META_MAX,
+ tb[TCA_IFE_METALST], NULL,
+ NULL);
+ if (err) {
+ kfree(p);
+ return err;
+ }
+ err = load_metalist(tb2, rtnl_held);
+ if (err) {
+ kfree(p);
+ return err;
+ }
+ }
+
index = parm->index;
err = tcf_idr_check_alloc(tn, &index, a, bind);
if (err < 0) {
@@ -569,15 +599,9 @@ static int tcf_ife_init(struct net *net,
}

if (tb[TCA_IFE_METALST]) {
- err = nla_parse_nested_deprecated(tb2, IFE_META_MAX,
- tb[TCA_IFE_METALST], NULL,
- NULL);
- if (err)
- goto metadata_parse_err;
err = populate_metalist(ife, tb2, exists, rtnl_held);
if (err)
goto metadata_parse_err;
-
} else {
/* if no passed metadata allow list or passed allow-all
* then here we process by adding as many supported metadatum