linux-kernel - Re: [PATCH -V19 00/15] Generic name to handle and open by handle syscalls

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]

Date:	Mon, 13 Sep 2010 16:59:22 +1000
From:	Neil Brown <neilb@...e.de>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	"Aneesh Kumar K. V" <aneesh.kumar@...ux.vnet.ibm.com>,
	hch@...radead.org, viro@...iv.linux.org.uk, adilger@....com,
	corbet@....net, npiggin@...nel.dk, hooanon05@...oo.co.jp,
	bfields@...ldses.org, linux-fsdevel@...r.kernel.org,
	sfrench@...ibm.com, philippe.deniel@....FR,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -V19 00/15] Generic name to handle and open by handle
 syscalls

On Mon, 13 Sep 2010 08:01:18 +0200
Miklos Szeredi <miklos@...redi.hu> wrote:

> On Mon, 13 Sep 2010, Aneesh Kumar K. V wrote:
> > As per your suggestion i started looking at handlefs details and below
> > is my take on the approach.
> > 
> > handlefs would be an internal kernel mount like pipefs and would have
> > inode object mapping to the returned file descriptor of
> > open_by_handle_at syscall for symlinks. For regular files we can do what
> > we already does and for symlinks we will create inodes in handlefs and
> > their inode operation will in turn result in call out of inode operations
> > of the actual symlinks. Based on the above
> > 
> > a) We still need open_by_handle_at syscall
> > b) We still need handle based link syscall, because we need to support
> >    creating hardlinks based on handle, and the existing linkat syscall
> >    takes the oldpath name.
> > c) We still need handle based readlink syscall, because the existing
> >    readlinkat syscall takes pathname.
> 
> You can implement ->read() on the symlink file instead.

I would suggest that is a much uglier hack than changed readlinkat to accept
a NULL pathname.

NeilBrown


> 
> > d) we can drop stat, chown and xattr syscall because they are introduced
> >    specially for symlinks as we don't allow open on symlinks.
> > e) It would be nice to have handle based stat syscall to avoid two
> >    syscall overhead for fetching file attributes when implementing a
> >    file server, where fetching file attribute is a common operation. 
> 
> Syscall overhead is generally insignificant compared to other effects.
> The server can also cache open files for commonly used handles.
> 
> > 
> > With the above from the current patch series we can drop chown and
> > xattr syscalls. Would it be ok if we get the series with the those two
> > syscall patches dropped upstream as i work on supporting symlinks with
> > handlefs approach ?
> 
> Try it.
> 
> Al seems to only be active to the outside world around the merge
> window, so that's the best time to ask him to pull.
> 
> Thanks,
> Miklos

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/