netdev - Re: [PATCHv2 net] sctp: use the correct skb for security_sctp_assoc

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Date:   Fri, 8 Apr 2022 16:26:12 +0200
From:   Ondrej Mosnacek <omosnace@...hat.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>,
        "linux-sctp @ vger . kernel . org" <linux-sctp@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCHv2 net] sctp: use the correct skb for security_sctp_assoc_request

On Thu, Apr 7, 2022 at 3:24 PM Xin Long <lucien.xin@...il.com> wrote:
> Yi Chen reported an unexpected sctp connection abort, and it occurred when
> COOKIE_ECHO is bundled with DATA Fragment by SCTP HW GSO. As the IP header
> is included in chunk->head_skb instead of chunk->skb, it failed to check
> IP header version in security_sctp_assoc_request().
>
> According to Ondrej, SELinux only looks at IP header (address and IPsec
> options) and XFRM state data, and these are all included in head_skb for
> SCTP HW GSO packets. So fix it by using head_skb when calling
> security_sctp_assoc_request() in processing COOKIE_ECHO.
>
> v1->v2:
>   - As Ondrej noticed, chunk->head_skb should also be used for
>     security_sctp_assoc_established() in sctp_sf_do_5_1E_ca().
>
> Fixes: e215dab1c490 ("security: call security_sctp_assoc_request in sctp_sf_do_5_1D_ce")
> Reported-by: Yi Chen <yiche@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  net/sctp/sm_statefuns.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index 7f342bc12735..52edee1322fc 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -781,7 +781,7 @@ enum sctp_disposition sctp_sf_do_5_1D_ce(struct net *net,
>                 }
>         }
>
> -       if (security_sctp_assoc_request(new_asoc, chunk->skb)) {
> +       if (security_sctp_assoc_request(new_asoc, chunk->head_skb ?: chunk->skb)) {
>                 sctp_association_free(new_asoc);
>                 return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
>         }
> @@ -932,7 +932,7 @@ enum sctp_disposition sctp_sf_do_5_1E_ca(struct net *net,
>
>         /* Set peer label for connection. */
>         if (security_sctp_assoc_established((struct sctp_association *)asoc,
> -                                           chunk->skb))
> +                                           chunk->head_skb ?: chunk->skb))
>                 return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
>
>         /* Verify that the chunk length for the COOKIE-ACK is OK.
> @@ -2262,7 +2262,7 @@ enum sctp_disposition sctp_sf_do_5_2_4_dupcook(
>         }
>
>         /* Update socket peer label if first association. */
> -       if (security_sctp_assoc_request(new_asoc, chunk->skb)) {
> +       if (security_sctp_assoc_request(new_asoc, chunk->head_skb ?: chunk->skb)) {
>                 sctp_association_free(new_asoc);
>                 return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
>         }
> --
> 2.31.1

FWIW:

Reviewed-by: Ondrej Mosnacek <omosnace@...hat.com>

Thanks!

-- 
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.