linux-kernel - Re: [PATCH v9 0/4] Add pidfd

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Message-ID: <20200110114056.zuc6ft2o4qspmbl6@wittgenstein>
Date:   Fri, 10 Jan 2020 12:40:57 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Sargun Dhillon <sargun@...gun.me>
Cc:     linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, tycho@...ho.ws, jannh@...gle.com,
        cyphar@...har.com, oleg@...hat.com, luto@...capital.net,
        viro@...iv.linux.org.uk, gpascutto@...illa.com,
        ealvarez@...illa.com, fweimer@...hat.com, jld@...illa.com,
        arnd@...db.de
Subject: Re: [PATCH v9 0/4] Add pidfd_getfd syscall

On Tue, Jan 07, 2020 at 09:54:49PM +0100, Christian Brauner wrote:
> On Tue, Jan 07, 2020 at 09:59:23AM -0800, Sargun Dhillon wrote:
> > This patchset introduces a mechanism (pidfd_getfd syscall) to get file
> > descriptors from other processes via pidfd. Although this can be achieved
> > using SCM_RIGHTS, and parasitic code injection, this offers a more
> > straightforward mechanism, with less overhead and complexity. The process
> > under manipulation's fd still remains valid, and unmodified by the
> > copy operation.
> > 
> > It introduces a flags field. The flags field is reserved a the moment,
> > but the intent is to extend it with the following capabilities:
> >  * Close the remote FD when copying it
> >  * Drop the cgroup data if it's a fd pointing a socket when copying it
> > 
> > The syscall numbers were chosen to be one greater than openat2.
> > 
> > Summary of history:
> > This initially started as a ptrace command. It did not require the process
> > to be stopped, and felt like kind of an awkward fit for ptrace. After that,
> > it moved to an ioctl on the pidfd. Given the core functionality, it made
> > sense to make it a syscall which did not require the process to be stopped.
> > 
> > Previous versions:
> >  V8: https://lore.kernel.org/lkml/20200103162928.5271-1-sargun@sargun.me/
> >  V7: https://lore.kernel.org/lkml/20191226180227.GA29389@ircssh-2.c.rugged-nimbus-611.internal/
> >  V6: https://lore.kernel.org/lkml/20191223210823.GA25083@ircssh-2.c.rugged-nimbus-611.internal/
> >  V5: https://lore.kernel.org/lkml/20191220232746.GA20215@ircssh-2.c.rugged-nimbus-611.internal/
> >  V4: https://lore.kernel.org/lkml/20191218235310.GA17259@ircssh-2.c.rugged-nimbus-611.internal/
> >  V3: https://lore.kernel.org/lkml/20191217005842.GA14379@ircssh-2.c.rugged-nimbus-611.internal/
> >  V2: https://lore.kernel.org/lkml/20191209070446.GA32336@ircssh-2.c.rugged-nimbus-611.internal/
> >  RFC V1: https://lore.kernel.org/lkml/20191205234450.GA26369@ircssh-2.c.rugged-nimbus-611.internal/
> 
> I don't see anything wrong with this series anymore:
> 
> Acked-by: Christian Brauner <christian.brauner@...ntu.com>
> 
> Other Acked-bys/Reviewed-bys and reviews of course strongly encouraged!
> Christian

Fyi, I'm waiting a few days on a reply from Al.
Depending on his input the intent rn is to move this into my for-next
early next week.

Christian