From: Paolo Abeni <pabeni@redhat.com>
To: Julian Anastasov <ja@ssi.bg>, netdev-bot+sashiko@kernel.org
Cc: pablo@netfilter.org, netfilter-devel@vger.kernel.org,
davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org,
edumazet@google.com, horms@kernel.org, fw@strlen.de
Subject: Re: [PATCH net 02/11] ipvs: fix buffer overflow when sending sync messages
Date: Tue, 29 Sep 2026 10:19:55 +0200 [thread overview]
Message-ID: <634b26a1-cf1f-46c0-8026-c9c08f398169@redhat.com> (raw)
In-Reply-To: <2aa8af69-3843-3ffd-cfa4-2daf3c949127@ssi.bg>
On 9/29/26 06:06, Julian Anastasov wrote:
>>> @@ -744,7 +749,7 @@ void ip_vs_sync_conn(struct netns_ipvs *ipvs, struct ip_vs_conn *cp, int pkts)
>>> s->v4.vaddr = cp->vaddr.ip;
>>> s->v4.daddr = cp->daddr.ip;
>>> }
>>> - if (cp->flags & IP_VS_CONN_F_SEQ_MASK) {
>>> + if (seq_mask) {
>>> *(p++) = IPVS_OPT_SEQ_DATA;
>>> *(p++) = sizeof(struct ip_vs_sync_conn_options);
>>> hton_seq(&cp->in_seq, (struct ip_vs_seq *)p);
>>
>> [Severity: Medium]
>> This is a pre-existing issue, not one introduced by this patch. The flags
>> are now a consistent snapshot, but the sequence data is still read
>> without cp->lock. Nothing orders that read against READ_ONCE(cp->flags).
>> Can the master send stale or half-updated ip_vs_seq values here?
>>
>> ip_vs_sync_conn() here only holds ipvs->sync_buff_lock. The same applies
>> to the memcpy() of cp->sync_conn_opt in ip_vs_sync_conn_v0().
>>
>> On the backup side, ip_vs_proc_conn() sets the SEQ bits in cp->flags under
>> cp->lock and drops the lock. Only after that does it copy the sequence
>> data, with no lock held:
>>
>> net/netfilter/ipvs/ip_vs_sync.c:ip_vs_proc_conn() {
>> ...
>> cp->flags = flags;
>> spin_unlock_bh(&cp->lock);
>> ...
>> if (opt) {
>> cp->in_seq = opt->in_seq;
>> cp->out_seq = opt->out_seq;
>> }
>> ...
>> }
>>
>> On a node running both the master and backup daemons, ip_vs_sync_conn()
>> could see seq_mask set and then send old or torn init_seq, delta and
>> previous_delta values. A peer with an app bound to that connection would
>> then apply the wrong TCP seq/ack adjustment after failover.
>
> Agreed, this can be improved to take a snapshot of
> flags and seqs together under lock. I'll request to drop
> this version, it is not urgent to apply it.
It looks like a respin of the PR is needed, I'll drop the revision from PW.
/P
next prev parent reply other threads:[~2026-09-29 8:20 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-27 22:08 [PATCH net 00/11] Netfilter/IPVS fixes for net Pablo Neira Ayuso
2026-09-27 22:08 ` [PATCH net 01/11] netfilter: ipset: do not update comments from kernel-side adds Pablo Neira Ayuso
2026-09-27 22:08 ` [PATCH net 02/11] ipvs: fix buffer overflow when sending sync messages Pablo Neira Ayuso
2026-09-28 23:55 ` netdev-bot+sashiko
2026-09-29 4:06 ` Julian Anastasov
2026-09-29 8:19 ` Paolo Abeni [this message]
2026-09-29 9:43 ` Pablo Neira Ayuso
2026-09-29 9:55 ` Paolo Abeni
2026-09-29 10:27 ` Pablo Neira Ayuso
2026-09-27 22:08 ` [PATCH net 03/11] netfilter: nft_flow_offload: drop flowtable reference on init error path Pablo Neira Ayuso
2026-09-28 23:55 ` netdev-bot+sashiko
2026-09-27 22:08 ` [PATCH net 04/11] ipvs: fix missing counter decrement in lblc Pablo Neira Ayuso
2026-09-27 22:08 ` [PATCH net 05/11] ipvs: bound LBLCR and LBLC cache growth Pablo Neira Ayuso
2026-09-27 22:08 ` [PATCH net 06/11] ipvs: do not create invisible templates Pablo Neira Ayuso
2026-09-27 22:08 ` [PATCH net 07/11] ipvs: filter some flags received in the backup server Pablo Neira Ayuso
2026-09-28 23:55 ` netdev-bot+sashiko
2026-09-29 4:17 ` Julian Anastasov
2026-09-27 22:08 ` [PATCH net 08/11] netfilter: nft_set_rbtree: skip transaction elements during GC Pablo Neira Ayuso
2026-09-28 23:55 ` netdev-bot+sashiko
2026-09-27 22:08 ` [PATCH net 09/11] netfilter: bpf: reject invalid NAT manipulation types Pablo Neira Ayuso
2026-09-27 22:08 ` [PATCH net 10/11] netfilter: flowtable: generalize pending status bit Pablo Neira Ayuso
2026-09-28 23:55 ` netdev-bot+sashiko
2026-09-27 22:08 ` [PATCH net 11/11] netfilter: flowtable: restore ieee80211 forward path Pablo Neira Ayuso
2026-09-29 2:11 ` [PATCH net 00/11] Netfilter/IPVS fixes for net Jakub Kicinski
2026-09-29 9:41 ` Pablo Neira Ayuso
2026-09-29 14:36 ` Julian Anastasov
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