2022-12-01 16:39:43

by Li Qiong

Subject: [PATCH] net: sched: fix a error path in fw_change()

The 'pfp' pointer could be null if can't find the target filter.
Check 'pfp' pointer and fix this error path.

Signed-off-by: Li Qiong <[email protected]>
---
net/sched/cls_fw.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
index a32351da968c..b898e4a81146 100644
--- a/net/sched/cls_fw.c
+++ b/net/sched/cls_fw.c
@@ -289,6 +289,12 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
if (pfp == f)
break;

+ if (!pfp) {
+ tcf_exts_destroy(&fnew->exts);
+ kfree(fnew);
+ return err;
+ }
+
RCU_INIT_POINTER(fnew->next, rtnl_dereference(pfp->next));
rcu_assign_pointer(*fp, fnew);
tcf_unbind_filter(tp, &f->res);
--
2.11.0

2022-12-03 05:31:23

by Jakub Kicinski

Subject: Re: [PATCH] net: sched: fix a error path in fw_change()

On Thu, 1 Dec 2022 23:15:32 +0800 Li Qiong wrote:
> The 'pfp' pointer could be null if can't find the target filter.
> Check 'pfp' pointer and fix this error path.

Sounds like a fix, we need a Fixes tag.

2022-12-03 20:41:00

by Cong Wang

Subject: Re: [PATCH] net: sched: fix a error path in fw_change()

On Thu, Dec 01, 2022 at 11:15:32PM +0800, Li Qiong wrote:
> The 'pfp' pointer could be null if can't find the target filter.
> Check 'pfp' pointer and fix this error path.

Did you see any actual kernel crash? And do you have a reproducer too?
Please include them if you do.

>
> Signed-off-by: Li Qiong <[email protected]>
> ---
> net/sched/cls_fw.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
> index a32351da968c..b898e4a81146 100644
> --- a/net/sched/cls_fw.c
> +++ b/net/sched/cls_fw.c
> @@ -289,6 +289,12 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
> if (pfp == f)
> break;
>
> + if (!pfp) {
> + tcf_exts_destroy(&fnew->exts);
> + kfree(fnew);
> + return err;


BTW, err is 0 here, you have to set some error here.

Thanks.

2022-12-05 03:10:06

by Li Qiong

Subject: Re: [PATCH] net: sched: fix a error path in fw_change()

在 2022年12月04日 03:46, Cong Wang 写道:
> On Thu, Dec 01, 2022 at 11:15:32PM +0800, Li Qiong wrote:
>> The 'pfp' pointer could be null if can't find the target filter.
>> Check 'pfp' pointer and fix this error path.
> Did you see any actual kernel crash? And do you have a reproducer too?
> Please include them if you do.
Found this by 'smatch' tool, I check and find it may be a real problem at the risk
of NULL pointer. Like 'fw_delete()', It checks 'pfp' and 'pfp == f' too.




>
>> Signed-off-by: Li Qiong <[email protected]>
>> ---
>> net/sched/cls_fw.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
>> index a32351da968c..b898e4a81146 100644
>> --- a/net/sched/cls_fw.c
>> +++ b/net/sched/cls_fw.c
>> @@ -289,6 +289,12 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
>> if (pfp == f)
>> break;
>>
>> + if (!pfp) {
>> + tcf_exts_destroy(&fnew->exts);
>> + kfree(fnew);
>> + return err;
>
> BTW, err is 0 here, you have to set some error here.
You are right, It should return '-EINVAL' -- can't get the target filter.



>
> Thanks.