Re: [PATCH] net/sctp: Prevent autoclose integer overflow in sctp_association_init()

[David Laight <david.laight.linux@gmail.com>]

On Thu, 19 Dec 2024 19:21:14 +0300
Nikolay Kuratov <kniv@yandex-team.ru> wrote:

> While by default max_autoclose equals to INT_MAX / HZ, one may set
> net.sctp.max_autoclose to UINT_MAX. There is code in
> sctp_association_init() that can consequently trigger overflow.
> 
> Cc: stable@vger.kernel.org
> Fixes: 9f70f46bd4c7 ("sctp: properly latch and use autoclose value from sock to association")
> Signed-off-by: Nikolay Kuratov <kniv@yandex-team.ru>
> ---
>  net/sctp/associola.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> index c45c192b7878..0b0794f164cf 100644
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -137,7 +137,8 @@ static struct sctp_association *sctp_association_init(
>  		= 5 * asoc->rto_max;
>  
>  	asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] = asoc->sackdelay;
> -	asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] = sp->autoclose * HZ;
> +	asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] =
> +		(unsigned long)sp->autoclose * HZ;

That doesn't fix 32bit systems.

Looking through sctp/structs.h there are a lot of 'long' used for
timeouts.
it can't be right that any of these change size between 32bit and 64bit.
So they should either be __u32 or __u64 (or similar).

	David

>  
>  	/* Initializes the timers */
>  	for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i)