linux-kernel - Re: [RFC][PATCH 1/5] exit: kill struct waitid

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Message-ID: <20190725100727.4ojpf2q53yl2owak@brauner.io>
Date:   Thu, 25 Jul 2019 12:07:28 +0200
From:   Christian Brauner <christian@...uner.io>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, arnd@...db.de, ebiederm@...ssion.com,
        keescook@...omium.org, joel@...lfernandes.org, tglx@...utronix.de,
        tj@...nel.org, dhowells@...hat.com, jannh@...gle.com,
        luto@...nel.org, akpm@...ux-foundation.org, cyphar@...har.com,
        torvalds@...ux-foundation.org, viro@...iv.linux.org.uk,
        kernel-team@...roid.com
Subject: Re: [RFC][PATCH 1/5] exit: kill struct waitid_info

On Thu, Jul 25, 2019 at 11:40:52AM +0200, Oleg Nesterov wrote:
> 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.

Will do.
Thanks, Oleg!
Christian