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

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Message #32 received at 39236 <at> debbugs.gnu.org (full text, mbox):

From: Rich Felker <dalias <at> libc.org>
To: Florian Weimer <fweimer <at> redhat.com>
Cc: musl <at> lists.openwall.com, 39236 <at> debbugs.gnu.org
Subject: Re: [musl] coreutils cp mishandles error return from lchmod
Date: Wed, 22 Jan 2020 15:56:05 -0500

On Wed, Jan 22, 2020 at 09:48:14PM +0100, Florian Weimer wrote:
> * Rich Felker:
> 
> >> Hmm.  The way I read the musl code, the O_PATH descriptor already
> >> exists.  At this point, you can just chmod the O_PATH descriptor, and
> >> have the kernel report EOPNOTSUPP if the file system does not support
> >> that.
> >
> > Oh, you mean the second one after it's already open? Maybe that's ok.
> 
> Yes, that's what I meant.
> 
> > I was concerned it might follow the link and chmod the target at that
> > point.
> 
> In my tests, it works.  I think it's also documented behavior for chown
> on these pseudo-files.

Do you know where we might find that documentation?

> I also verified that closing an O_PATH descriptor does not release POSIX
> advisory locks for the same file.  But I'm wondering if there's still
> something we are missing.

Thanks, I hadn't thought to check that, but wouldn't have expected it
to be a problem since O_PATH is not actually open to the file.

Rich

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