linux-kernel - Re: [PATCH 1/2] vfs: implement fchmodat2() syscall

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Message-ID: <32c7aa8f-e881-d85c-6508-fb0e58922a41@redhat.com>
Date:   Tue, 11 Apr 2017 13:08:52 -0500
From:   Eric Blake <eblake@...hat.com>
To:     Colin Walters <walters@...bum.org>, Greg Kurz <groug@...d.org>,
        viro@...iv.linux.org.uk
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] vfs: implement fchmodat2() syscall

On 04/11/2017 01:07 PM, Eric Blake wrote:

> 
> 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.
> 

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



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