GNU bug report logs - #39236
[musl] coreutils cp mishandles error return from lchmod

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From: Rich Felker <dalias <at> libc.org>
To: Florian Weimer <fw <at> deneb.enyo.de>
Cc: Florian Weimer <fweimer <at> redhat.com>, musl <at> lists.openwall.com, Paul Eggert <eggert <at> cs.ucla.edu>, Gnulib bugs <bug-gnulib <at> gnu.org>, 39236 <at> debbugs.gnu.org
Subject: bug#39236: [musl] coreutils cp mishandles error return from lchmod
Date: Wed, 12 Feb 2020 08:05:55 -0500

On Wed, Feb 12, 2020 at 12:50:19PM +0100, Florian Weimer wrote:
> * Paul Eggert:
> 
> > On 1/22/20 2:05 PM, Rich Felker wrote:
> >> I think we're approaching a consensus that glibc should fix this too,
> >> so then it would just be gnulib matching the fix.
> >
> > I installed the attached patch to Gnulib in preparation for the upcoming 
> > glibc fix. The patch causes fchmodat with AT_SYMLINK_NOFOLLOW to work on 
> > non-symlinks, and similarly for lchmod on non-symlinks. The idea is to 
> > avoid this sort of problem in the future, and to let Coreutils etc. work 
> > on older platforms as if glibc 2.32 (or whatever) is already in place.
> 
> The lchmod implementation based on /proc tickles an XFS bug:
> 
>   <https://sourceware.org/ml/libc-alpha/2020-02/msg00467.html>

Uhg, why does Linux even let the fs driver see whether the chmod is
being performed via a filename, O_PATH fd, or magic symlink in /proc?
It should just be an operation on the inode.

Rich

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