linux-kernel - Re: [PATCH] audit: move calcs after alloc and check when logging set loginuid

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Message-ID: <CAGH-KgtF3XDPuyM3qeztEfg4Oh2hP8EouKhuVBKAfzapohPQiw@mail.gmail.com>
Date:	Tue, 28 Jun 2016 15:42:51 -0400
From:	Paul Moore <pmoore@...hat.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	peter@...leysoftware.com, sgrubb@...hat.com, eparis@...hat.com
Subject: Re: [PATCH] audit: move calcs after alloc and check when logging set loginuid

On Tue, Jun 28, 2016 at 12:06 PM, Richard Guy Briggs <rgb@...hat.com> wrote:
> Move the calculations of values after the allocation in case the
> allocation fails.  This avoids wasting effort in the rare case that it
> fails, but more importantly saves us extra logic to release the tty ref.
>
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
>  kernel/auditsc.c |    7 ++++---
>  1 files changed, 4 insertions(+), 3 deletions(-)

Most importantly it keeps us from leaking a kref, which we currently
do if audit_log_start() fails.

Applied to audit#stable-4.7 and I'll be pushing this to Linus once
I've had a chance to see if your other patch is worth pushing during
the 4.7-rc cycle too.

> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 71e14d8..33dafa7 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -1985,14 +1985,15 @@ static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t kloginuid,
>         if (!audit_enabled)
>                 return;
>
> +       ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
> +       if (!ab)
> +               return;
> +
>         uid = from_kuid(&init_user_ns, task_uid(current));
>         oldloginuid = from_kuid(&init_user_ns, koldloginuid);
>         loginuid = from_kuid(&init_user_ns, kloginuid),
>         tty = audit_get_tty(current);
>
> -       ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
> -       if (!ab)
> -               return;
>         audit_log_format(ab, "pid=%d uid=%u", task_pid_nr(current), uid);
>         audit_log_task_context(ab);
>         audit_log_format(ab, " old-auid=%u auid=%u tty=%s old-ses=%u ses=%u res=%d",
> --
> 1.7.1
>



-- 
paul moore
security @ redhat