linux-kernel - Re: [PATCH] vfs: add fchmodat2 syscall

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200910154516.GH3265@brightrain.aerifal.cx>
Date:   Thu, 10 Sep 2020 11:45:17 -0400
From:   Rich Felker <dalias@...c.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: add fchmodat2 syscall

On Thu, Sep 10, 2020 at 04:18:28PM +0100, Al Viro wrote:
> On Thu, Sep 10, 2020 at 10:23:37AM -0400, Rich Felker wrote:
> 
> > It was determined (see glibc issue #14578 and commit a492b1e5ef) that,
> > on some filesystems, performing chmod on the link itself produces a
> > change in the inode's access mode, but returns an EOPNOTSUPP error.
> 
> Which filesystem types are those?

It's been a long time and I don't know if the details were recorded.
It was reported for xfs but I believe we later found it happening for
others. See:

https://sourceware.org/bugzilla/show_bug.cgi?id=14578#c17
https://sourceware.org/legacy-ml/libc-alpha/2020-02/msg00467.html

and especially:

https://sourceware.org/legacy-ml/libc-alpha/2020-02/msg00518.html

where Christoph seems to have endorsed the approach in my patch. I'm
fine with doing it differently if you'd prefer, though.

Rich