Re: [PATCH net] net: sctp: check proc_dointvec result in proc_sctp_do_auth

[Vlad Yasevich <vyasevich@gmail.com>]

On 06/18/2014 05:46 PM, Daniel Borkmann wrote:
> When writing to the sysctl field net.sctp.auth_enable, it can well
> be that the user buffer we handed over to proc_dointvec() via
> proc_sctp_do_auth() handler contains something other than integers.
> 
> In that case, we would set an uninitialized 4-byte value from the
> stack to net->sctp.auth_enable that can be leaked back when reading
> the sysctl variable, and it can unintentionally turn auth_enable
> on/off based on the stack content since auth_enable is interpreted
> as a boolean.
> 
> Fix it up by making sure proc_dointvec() returned sucessfully.
> 
> Fixes: b14878ccb7fa ("net: sctp: cache auth_enable per endpoint")
> Reported-by: Florian Westphal <fwestpha@redhat.com>
> Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
> ---
>  net/sctp/sysctl.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
> index dcb1959..8a5b5c2 100644
> --- a/net/sctp/sysctl.c
> +++ b/net/sctp/sysctl.c
> @@ -444,8 +444,7 @@ static int proc_sctp_do_auth(struct ctl_table *ctl, int write,
>  		tbl.data = &net->sctp.auth_enable;
>  
>  	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
> -
> -	if (write) {
> +	if (write && ret == 0) {
>  		struct sock *sk = net->sctp.ctl_sock;
>  
>  		net->sctp.auth_enable = new_value;
> 

Acked-by: Vlad Yasevich <vyasevich@gmail.com>

-vlad