netdev - Re: [PATCH net-next v5 3/5] net/sched: act_pedit: check static offsets a priori

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Date:   Tue, 25 Apr 2023 09:27:32 -0300
From:   Pedro Tammela <pctammela@...atatu.com>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, simon.horman@...igine.com
Subject: Re: [PATCH net-next v5 3/5] net/sched: act_pedit: check static
 offsets a priori

On 25/04/2023 09:13, Ido Schimmel wrote:
> On Fri, Apr 21, 2023 at 06:25:15PM -0300, Pedro Tammela wrote:
>> diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
>> index 24976cd4e4a2..cc4dfb01c6c7 100644
>> --- a/net/sched/act_pedit.c
>> +++ b/net/sched/act_pedit.c
>> @@ -251,8 +251,16 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
>>   	memcpy(nparms->tcfp_keys, parm->keys, ksize);
>>   
>>   	for (i = 0; i < nparms->tcfp_nkeys; ++i) {
>> +		u32 offmask = nparms->tcfp_keys[i].offmask;
>>   		u32 cur = nparms->tcfp_keys[i].off;
>>   
>> +		/* The AT option can be added to static offsets in the datapath */
>> +		if (!offmask && cur % 4) {
>> +			NL_SET_ERR_MSG_MOD(extack, "Offsets must be on 32bit boundaries");
>> +			ret = -EINVAL;
>> +			goto put_chain;
> 
> I think this leaks 'nparms->tcfp_keys'. See full syzkaller report here
> [1].
> 


Hi Ido,

Indeed! Thanks for the report.
Can you run the syzkaller corpus with the following patch?

---

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index fb93d4c1faca..fc945c7e4123 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -258,7 +258,7 @@ static int tcf_pedit_init(struct net *net, struct 
nlattr *nla,
                 if (!offmask && cur % 4) {
                         NL_SET_ERR_MSG_MOD(extack, "Offsets must be on 
32bit boundaries");
                         ret = -EINVAL;
-                       goto put_chain;
+                       goto out_free_keys;
                 }

                 /* sanitize the shift value for any later use */
@@ -291,6 +291,8 @@ static int tcf_pedit_init(struct net *net, struct 
nlattr *nla,

         return ret;

+out_free_keys:
+       kfree(nparms->tcfp_keys);
  put_chain:
         if (goto_ch)
                 tcf_chain_put_by_act(goto_ch);