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act_ife: load meta modules before tcf_idr_check_alloc() 

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: 0190c1d452 ("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>
This commit is contained in:
Cong Wang 2020-09-03 19:10:11 -07:00 committed by Jakub Kicinski
parent c2b947879c
commit cc8e58f832
1 changed files with 34 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
net/sched/act_ife.c
View File

@ -436,6 +436,25 @@ static void tcf_ife_cleanup(struct tc_action *a)
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_ife_info *ife, struct nlattr **tb,
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;
@ -509,6 +524,21 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
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) {
@ -570,15 +600,9 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
}
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