netdev - Re: [PATCH] sctp: socket.c validate sprstat

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Date:   Sat, 27 Oct 2018 22:43:43 +0200
From:   Tomas Bortoli <tomasbortoli@...il.com>
To:     vyasevich@...il.com, nhorman@...driver.com,
        marcelo.leitner@...il.com
Cc:     davem@...emloft.net, linux-sctp@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sctp: socket.c validate sprstat_policy

On 10/27/18 10:20 PM, Tomas Bortoli wrote:
> It is possible to perform out-of-bound reads on
> sctp_getsockopt_pr_streamstatus() and on
> sctp_getsockopt_pr_assocstatus() by passing from userspace a
> sprstat_policy that overflows the abandoned_sent/abandoned_unsent
> fixed length arrays. The over-read data are directly copied/leaked
> to userspace.
> 
> Signed-off-by: Tomas Bortoli <tomasbortoli@...il.com>
> Reported-by: syzbot+5da0d0a72a9e7d791748@...kaller.appspotmail.com
> ---
> v2 - added forgot ||
> 
>  net/sctp/socket.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index fc0386e8ff23..5290b8bd40c8 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -7083,7 +7083,8 @@ static int sctp_getsockopt_pr_assocstatus(struct sock *sk, int len,
>  	}
>  
>  	policy = params.sprstat_policy;
> -	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)))
> +	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)) ||
> +	    __SCTP_PR_INDEX(policy) > SCTP_PR_INDEX(MAX))
>  		goto out;
>  
>  	asoc = sctp_id2assoc(sk, params.sprstat_assoc_id);
> @@ -7142,7 +7143,8 @@ static int sctp_getsockopt_pr_streamstatus(struct sock *sk, int len,
>  	}
>  
>  	policy = params.sprstat_policy;
> -	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)))
> +	if (!policy || (policy & ~(SCTP_PR_SCTP_MASK | SCTP_PR_SCTP_ALL)) ||
> +	    __SCTP_PR_INDEX(policy) > SCTP_PR_INDEX(MAX))
>  		goto out;
>  
>  	asoc = sctp_id2assoc(sk, params.sprstat_assoc_id);
> 

I just realized we also have to check for less than 0 indexes..