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@xxxxxxxxxx>
> Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxxx>
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