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Subject: Re: [PATCH 1/2] vfs: implement fchmodat2() syscall
To: Colin Walters <walters@verbum.org>, Greg Kurz <groug@kaod.org>,
        viro@zeniv.linux.org.uk
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Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
From: Eric Blake <eblake@redhat.com>
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Date: Tue, 11 Apr 2017 13:08:52 -0500
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From: Eric Blake <eblake@redhat.com>
To: Colin Walters <walters@verbum.org>, Greg Kurz <groug@kaod.org>,
 viro@zeniv.linux.org.uk
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Message-ID: <32c7aa8f-e881-d85c-6508-fb0e58922a41@redhat.com>
Subject: Re: [PATCH 1/2] vfs: implement fchmodat2() syscall
References: <148830142269.7103.7429913851447595016.stgit@bahia>
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On 04/11/2017 01:07 PM, Eric Blake wrote:

>=20
> But even if using open(O_PATH)/fchmod() works, it is not immediately
> obvious whether it can catch all the same cases that chmodat(O_NOFOLLOW=
)

Typo; I obviously meant fchmodat(AT_SYMLINK_NOFOLLOW)

> would cover, as there are cases where you have permissions to change
> mode bits but not open() the file for reading or writing.  And even if
> it gets rid of a TOCTTOU race, it still is a 2-syscall hit rather than
> an atomic single syscall.
>=20

--=20
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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