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

From: Paul Moore
Date: Tue Jun 28 2016 - 15:42:57 EST


On Tue, Jun 28, 2016 at 12:06 PM, Richard Guy Briggs <rgb@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> 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