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Message-ID: <CAHC9VhR_VdOzsb3TeokfKN+SoRE4aN95aMDyNaQ-TKUoW0C0zg@mail.gmail.com>
Date: Thu, 30 Nov 2017 11:57:59 -0500
From: Paul Moore <paul@...l-moore.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: Casey Schaufler <casey@...aufler-ca.com>,
James Morris <james.l.morris@...cle.com>,
netdev@...r.kernel.org, Stephen Smalley <sds@...ho.nsa.gov>,
selinux@...ho.nsa.gov, LSM <linux-security-module@...r.kernel.org>
Subject: Re: [BUG] kernel stack corruption during/after Netlabel error
On Thu, Nov 30, 2017 at 7:47 AM, Paul Moore <paul@...l-moore.com> wrote:
> On Thu, Nov 30, 2017 at 5:50 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> On Wed, 2017-11-29 at 19:16 -0800, Casey Schaufler wrote:
>>> On 11/29/2017 4:31 PM, James Morris wrote:
>>> > On Wed, 29 Nov 2017, Casey Schaufler wrote:
>>> >
>>> > > I see that there is a proposed fix later in the thread, but I
>>> > > don't see
>>> > > the patch. Could you send it to me, so I can try it on my
>>> > > problem?
>>> >
>>> > Forwarded off-list.
>>>
>>> The patch does fix the problem I was seeing in Smack.
>>
>> Can you guys test the following more complete patch ?
>>
>> It should cover IPv4 and IPv6, and also the corner cases.
>>
>> ( Note that I squashed ipv6 fix in https://patchwork.ozlabs.org/patch/8
>> 42844/ that I spotted while cooking this patch )
>
> Building a test kernel now, although it make take me a few hours to
> test it due to some commitments this morning.
I just realized I forgot to enable KASAN in the build, but I can
verify that the patch doesn't break anything in the selinux-testsuite.
Tested-by: Paul Moore <paul@...l-moore.com>
>> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
>> index c6bc0c4d19c624888b0d0b5a4246c7183edf63f5..77ea45da0fe9c746907a312989658af3ad3b198d 100644
>> --- a/net/ipv4/tcp_ipv4.c
>> +++ b/net/ipv4/tcp_ipv4.c
>> @@ -1591,6 +1591,34 @@ int tcp_filter(struct sock *sk, struct sk_buff *skb)
>> }
>> EXPORT_SYMBOL(tcp_filter);
>>
>> +static void tcp_v4_restore_cb(struct sk_buff *skb)
>> +{
>> + memmove(IPCB(skb), &TCP_SKB_CB(skb)->header.h4,
>> + sizeof(struct inet_skb_parm));
>> +}
>> +
>> +static void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph,
>> + const struct tcphdr *th)
>> +{
>> + /* This is tricky : We move IPCB at its correct location into TCP_SKB_CB()
>> + * barrier() makes sure compiler wont play fool^Waliasing games.
>> + */
>> + memmove(&TCP_SKB_CB(skb)->header.h4, IPCB(skb),
>> + sizeof(struct inet_skb_parm));
>> + barrier();
>> +
>> + TCP_SKB_CB(skb)->seq = ntohl(th->seq);
>> + TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
>> + skb->len - th->doff * 4);
>> + TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
>> + TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
>> + TCP_SKB_CB(skb)->tcp_tw_isn = 0;
>> + TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph);
>> + TCP_SKB_CB(skb)->sacked = 0;
>> + TCP_SKB_CB(skb)->has_rxtstamp =
>> + skb->tstamp || skb_hwtstamps(skb)->hwtstamp;
>> +}
>> +
>> /*
>> * From tcp_input.c
>> */
>> @@ -1631,24 +1659,6 @@ int tcp_v4_rcv(struct sk_buff *skb)
>>
>> th = (const struct tcphdr *)skb->data;
>> iph = ip_hdr(skb);
>> - /* This is tricky : We move IPCB at its correct location into TCP_SKB_CB()
>> - * barrier() makes sure compiler wont play fool^Waliasing games.
>> - */
>> - memmove(&TCP_SKB_CB(skb)->header.h4, IPCB(skb),
>> - sizeof(struct inet_skb_parm));
>> - barrier();
>> -
>> - TCP_SKB_CB(skb)->seq = ntohl(th->seq);
>> - TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
>> - skb->len - th->doff * 4);
>> - TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
>> - TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
>> - TCP_SKB_CB(skb)->tcp_tw_isn = 0;
>> - TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph);
>> - TCP_SKB_CB(skb)->sacked = 0;
>> - TCP_SKB_CB(skb)->has_rxtstamp =
>> - skb->tstamp || skb_hwtstamps(skb)->hwtstamp;
>> -
>> lookup:
>> sk = __inet_lookup_skb(&tcp_hashinfo, skb, __tcp_hdrlen(th), th->source,
>> th->dest, sdif, &refcounted);
>> @@ -1679,14 +1689,19 @@ int tcp_v4_rcv(struct sk_buff *skb)
>> sock_hold(sk);
>> refcounted = true;
>> nsk = NULL;
>> - if (!tcp_filter(sk, skb))
>> + if (!tcp_filter(sk, skb)) {
>> + th = (const struct tcphdr *)skb->data;
>> + iph = ip_hdr(skb);
>> + tcp_v4_fill_cb(skb, iph, th);
>> nsk = tcp_check_req(sk, skb, req, false);
>> + }
>> if (!nsk) {
>> reqsk_put(req);
>> goto discard_and_relse;
>> }
>> if (nsk == sk) {
>> reqsk_put(req);
>> + tcp_v4_restore_cb(skb);
>> } else if (tcp_child_process(sk, nsk, skb)) {
>> tcp_v4_send_reset(nsk, skb);
>> goto discard_and_relse;
>> @@ -1712,6 +1727,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
>> goto discard_and_relse;
>> th = (const struct tcphdr *)skb->data;
>> iph = ip_hdr(skb);
>> + tcp_v4_fill_cb(skb, iph, th);
>>
>> skb->dev = NULL;
>>
>> @@ -1742,6 +1758,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
>> if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
>> goto discard_it;
>>
>> + tcp_v4_fill_cb(skb, iph, th);
>> +
>> if (tcp_checksum_complete(skb)) {
>> csum_error:
>> __TCP_INC_STATS(net, TCP_MIB_CSUMERRORS);
>> @@ -1768,6 +1786,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
>> goto discard_it;
>> }
>>
>> + tcp_v4_fill_cb(skb, iph, th);
>> +
>> if (tcp_checksum_complete(skb)) {
>> inet_twsk_put(inet_twsk(sk));
>> goto csum_error;
>> @@ -1784,6 +1804,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
>> if (sk2) {
>> inet_twsk_deschedule_put(inet_twsk(sk));
>> sk = sk2;
>> + tcp_v4_restore_cb(skb);
>> refcounted = false;
>> goto process;
>> }
>> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
>> index 6bb98c93edfe2ed2f16fe5229605f8108cfc7f9a..1f04ec0e4a7aa2c11b8ee27cbdd4067b5bcf32e5 100644
>> --- a/net/ipv6/tcp_ipv6.c
>> +++ b/net/ipv6/tcp_ipv6.c
>> @@ -1454,7 +1454,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>> struct sock *nsk;
>>
>> sk = req->rsk_listener;
>> - tcp_v6_fill_cb(skb, hdr, th);
>> if (tcp_v6_inbound_md5_hash(sk, skb)) {
>> sk_drops_add(sk, skb);
>> reqsk_put(req);
>> @@ -1467,8 +1466,12 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>> sock_hold(sk);
>> refcounted = true;
>> nsk = NULL;
>> - if (!tcp_filter(sk, skb))
>> + if (!tcp_filter(sk, skb)) {
>> + th = (const struct tcphdr *)skb->data;
>> + hdr = ipv6_hdr(skb);
>> + tcp_v6_fill_cb(skb, hdr, th);
>> nsk = tcp_check_req(sk, skb, req, false);
>> + }
>> if (!nsk) {
>> reqsk_put(req);
>> goto discard_and_relse;
>> @@ -1492,8 +1495,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>> if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
>> goto discard_and_relse;
>>
>> - tcp_v6_fill_cb(skb, hdr, th);
>> -
>> if (tcp_v6_inbound_md5_hash(sk, skb))
>> goto discard_and_relse;
>>
>> @@ -1501,6 +1502,7 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>> goto discard_and_relse;
>> th = (const struct tcphdr *)skb->data;
>> hdr = ipv6_hdr(skb);
>> + tcp_v6_fill_cb(skb, hdr, th);
>>
>> skb->dev = NULL;
>>
>> @@ -1590,7 +1592,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
>> tcp_v6_timewait_ack(sk, skb);
>> break;
>> case TCP_TW_RST:
>> - tcp_v6_restore_cb(skb);
>> tcp_v6_send_reset(sk, skb);
>> inet_twsk_deschedule_put(inet_twsk(sk));
>> goto discard_it;
>>
>>
>>
>
>
>
> --
> paul moore
> www.paul-moore.com
--
paul moore
www.paul-moore.com
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