Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 25 Jul 2019 11:40:52 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Christian Brauner <christian@brauner.io>
Cc:     linux-kernel@vger.kernel.org, arnd@arndb.de, ebiederm@xmission.com,
        keescook@chromium.org, joel@joelfernandes.org, tglx@linutronix.de,
        tj@kernel.org, dhowells@redhat.com, jannh@google.com,
        luto@kernel.org, akpm@linux-foundation.org, cyphar@cyphar.com,
        torvalds@linux-foundation.org, viro@zeniv.linux.org.uk,
        kernel-team@android.com
Subject: Re: [RFC][PATCH 1/5] exit: kill struct waitid_info
Message-ID: <20190725094051.GC4707@redhat.com>
References: <20190724144651.28272-1-christian@brauner.io>
 <20190724144651.28272-2-christian@brauner.io>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190724144651.28272-2-christian@brauner.io>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 07/24, Christian Brauner wrote:
>
> Note that this changes how struct siginfo is filled in for users of
> waitid.

Namely, copy_siginfo_to_user() will nullify the extra SI_EXPANSION_SIZE
bytes + 2*sizeof(__ARCH_SI_CLOCK_T) from _sigchld (waitid doesn't report
utime/stime in siginfo).

Looks correct... even the compat case, but please double-check
copy_siginfo_to_user32/siginfo_layout. Looks like both SIL_KILL and
SIL_CHLD cases are fine in that this patch can't add other user-visible
changes, but I could easily miss something.

> In case
> anyone relies on the old behavior we can just revert

we won't need to rever the whole patch, we can just replace
copy_siginfo_to_user() with copy_to_user(offsetof(si_utime)).

I see you are going to update the changelog and resend, feel free to add
my reviewed-by.

Oleg.