[PATCHv2 net] sctp: use the correct skb for security_sctp_assoc_request

[PATCHv2 net] sctp: use the correct skb for security_sctp_assoc_request

[Xin Long]

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@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.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

Re: [PATCHv2 net] sctp: use the correct skb for security_sctp_assoc_request

[Ondrej Mosnacek]

On Thu, Apr 7, 2022 at 3:24 PM Xin Long <lucien.xin@gmail.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@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.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@redhat.com>

Thanks!

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

Re: [PATCHv2 net] sctp: use the correct skb for security_sctp_assoc_request

[Marcelo Ricardo Leitner]

On Thu, Apr 07, 2022 at 09:24:22AM -0400, Xin Long 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@redhat.com>
> Signed-off-by: Xin Long <lucien.xin@gmail.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Re: [PATCHv2 net] sctp: use the correct skb for security_sctp_assoc_request

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Thu,  7 Apr 2022 09:24:22 -0400 you 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.
> 
> [...]

Here is the summary with links:
  - [PATCHv2,net] sctp: use the correct skb for security_sctp_assoc_request
    https://git.kernel.org/netdev/net/c/e2d88f9ce678

You are awesome, thank you!
-- 
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