[Lucid,CVE,2/2] sctp: Use correct sideffect command in duplicate cookie handling

From: Vlad Yasevich <vyasevich@gmail.com>

CVE-2013-2206

BugLink: http://bugs.launchpad.net/bugs/1194445

When SCTP is done processing a duplicate cookie chunk, it tries
to delete a newly created association.  For that, it has to set
the right association for the side-effect processing to work.
However, when it uses the SCTP_CMD_NEW_ASOC command, that performs
more work then really needed (like hashing the associationa and
assigning it an id) and there is no point to do that only to
delete the association as a next step.  In fact, it also creates
an impossible condition where an association may be found by
the getsockopt() call, and that association is empty.  This
causes a crash in some sctp getsockopts.

The solution is rather simple.  We simply use SCTP_CMD_SET_ASOC
command that doesn't have all the overhead and does exactly
what we need.

Reported-by: Karl Heiss <kheiss@gmail.com>
Tested-by: Karl Heiss <kheiss@gmail.com>
CC: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit f2815633504b442ca0b0605c16bf3d88a3a0fcea)
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 net/sctp/sm_statefuns.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On 08/01/2013 02:32 PM, Luis Henriques wrote:
> From: Vlad Yasevich <vyasevich@gmail.com>
>
> CVE-2013-2206
>
> BugLink: http://bugs.launchpad.net/bugs/1194445
>
> When SCTP is done processing a duplicate cookie chunk, it tries
> to delete a newly created association.  For that, it has to set
> the right association for the side-effect processing to work.
> However, when it uses the SCTP_CMD_NEW_ASOC command, that performs
> more work then really needed (like hashing the associationa and
> assigning it an id) and there is no point to do that only to
> delete the association as a next step.  In fact, it also creates
> an impossible condition where an association may be found by
> the getsockopt() call, and that association is empty.  This
> causes a crash in some sctp getsockopts.
>
> The solution is rather simple.  We simply use SCTP_CMD_SET_ASOC
> command that doesn't have all the overhead and does exactly
> what we need.
>
> Reported-by: Karl Heiss <kheiss@gmail.com>
> Tested-by: Karl Heiss <kheiss@gmail.com>
> CC: Neil Horman <nhorman@tuxdriver.com>
> Signed-off-by: Vlad Yasevich <vyasevich@gmail.com>
> Acked-by: Neil Horman <nhorman@tuxdriver.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> (cherry picked from commit f2815633504b442ca0b0605c16bf3d88a3a0fcea)
> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
> ---
>   net/sctp/sm_statefuns.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> index 9e4e846..486df56 100644
> --- a/net/sctp/sm_statefuns.c
> +++ b/net/sctp/sm_statefuns.c
> @@ -2045,7 +2045,7 @@ sctp_disposition_t sctp_sf_do_5_2_4_dupcook(const struct sctp_endpoint *ep,
>   	}
>
>   	/* Delete the tempory new association. */
> -	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(new_asoc));
> +	sctp_add_cmd_sf(commands, SCTP_CMD_SET_ASOC, SCTP_ASOC(new_asoc));
>   	sctp_add_cmd_sf(commands, SCTP_CMD_DELETE_TCB, SCTP_NULL());
>
>   	/* Restore association pointer to provide SCTP command interpeter
>