Re: [PATCH 1/2 nf] netfilter: seqadj: Fix some possible panics of seqadj when mem is exhausted

Hi Liping,

On Fri, Sep 2, 2016 at 12:50 PM, Liping Zhang [off-list ref] wrote:

Hi Feng,
2016-09-02 9:48 GMT+08:00  [off-list ref]:

quoted

From: Gao Feng <redacted>

@@ -171,6 +176,11 @@ int nf_ct_seq_adjust(struct sk_buff *skb,
        struct nf_ct_seqadj *this_way, *other_way;
        int res;

+       if (unlikely(!seqadj)) {

IPS_SEQ_ADJUST_BIT will be tested before we call nf_ct_seq_adjust(),
so I think seqadj
will never be NULL here.

Thanks. I didn't check  IPS_SEQ_ADJUST_BIT  flag.

quoted

+               WARN_ONCE(1, "Missing nfct_seqadj_ext_add() setup call\n");
+               return 0;
+       }
+
        this_way  = &seqadj->seq[dir];
        other_way = &seqadj->seq[!dir];

@@ -218,8 +228,10 @@ s32 nf_ct_seq_offset(const struct nf_conn *ct,
        struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
        struct nf_ct_seqadj *this_way;

-       if (!seqadj)
+       if (unlikely(!seqadj)) {
+               WARN_ONCE(1, "Missing nfct_seqadj_ext_add() setup call\n");

But in nf_ct_seq_offset, seqadj is likely to be NULL, see the function
call path:
tcp_packet->tcp_in_window->nf_ct_seq_offset, so WARN_ONCE seems unnecessary.

quoted

                return 0;
+       }

Get it. It could be NULL.

Then only nf_ct_seqadj_init is necessary to check seqadj.
I will update this patch.

Regards
Feng