netdev - Re: [PATCH net] net: sctp: check proc_dointvec result in proc_sctp_do

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Date:	Thu, 19 Jun 2014 09:05:19 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-sctp@...r.kernel.org
Subject: Re: [PATCH net] net: sctp: check proc_dointvec result in
 proc_sctp_do_auth

On Wed, Jun 18, 2014 at 11:46:31PM +0200, 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@...hat.com>
> Signed-off-by: Daniel Borkmann <dborkman@...hat.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;
> -- 
> 1.7.11.7
> 
> --
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> 

Acked-by: Neil Horman <nhorman@...driver.com>

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