inline
On Tue, Sep 6, 2016 at 6:17 PM, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote:
> On Tue, Sep 06, 2016 at 09:57:23AM +0800, fgao@xxxxxxxxxx wrote:
>> From: Gao Feng <fgao@xxxxxxxxxx>
>>
>> When memory is exhausted, nfct_seqadj_ext_add may fail to add the seqadj
>> extension. But the function nf_ct_seqadj_init doesn't check if get valid
>> seqadj pointer by the nfct_seqadj.
>>
>> Now drop the packet directly when fail to add seqadj extension to avoid
>> dereference NULL pointer in nf_ct_seqadj_init.
>>
>> Signed-off-by: Gao Feng <fgao@xxxxxxxxxx>
>> ---
>> v4: Drop the packet directly when fail to add seqadj extension;
>> v3: Remove the warning log when seqadj is null;
>> v2: Remove the unnessary seqadj check in nf_ct_seq_adjust
>> v1: Initial patch
>>
>> net/netfilter/nf_conntrack_core.c | 6 +++++-
>> net/netfilter/nf_nat_core.c | 3 ++-
>> 2 files changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
>> index dd2c43a..dfa76ce 100644
>> --- a/net/netfilter/nf_conntrack_core.c
>> +++ b/net/netfilter/nf_conntrack_core.c
>> @@ -1036,7 +1036,11 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
>> return (struct nf_conntrack_tuple_hash *)ct;
>>
>> if (tmpl && nfct_synproxy(tmpl)) {
>> - nfct_seqadj_ext_add(ct);
>> + if (!nfct_seqadj_ext_add(ct)) {
>> + nf_conntrack_free(ct);
>> + pr_debug("Can't add seqadj extension\n");
>> + return NULL;
>> + }
>> nfct_synproxy_ext_add(ct);
>
> I think this is part of the same logical change, ie. nf_ct_ext_add()
> returns NULL, then I would also fix nfct_synproxy_ext_add() in this
> go.
>
Sorry, I am not clear well.
Need I modify the logic of this part?
>> }
>>
>> diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
>> index de31818..b82282a 100644
>> --- a/net/netfilter/nf_nat_core.c
>> +++ b/net/netfilter/nf_nat_core.c
>> @@ -441,7 +441,8 @@ nf_nat_setup_info(struct nf_conn *ct,
>> ct->status |= IPS_DST_NAT;
>>
>> if (nfct_help(ct))
>> - nfct_seqadj_ext_add(ct);
>> + if (!nfct_seqadj_ext_add(ct))
>> + return NF_DROP;
>
> ctnetlink may have created a conntrack with seqadj in place by when we
> call nf_nat_setup_info() so NF_ACCEPT would be more conservative, eg.
> via conntrackd state synchronization.
>
> Actually, after a quick look at ctnetlink, I don't see any any call to
> nfct_seqadj_ext_add() from there, so I suspect this is broken since
> SYNPROXY was introduced. It would be great if you can review this and
> send us patches to fix this, if indeed needed.
>
> Thanks!
Let me confirm the problem, or I am afraid I would misunderstand our meaning.
This patch only need to modify the "NF_DROP" to "NF_ACCEPT", is it?
Then I could commit another patch to fix the ctnetlink lost nfct_seqadj_ext_add.
Best Regards
Feng
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