linux-kernel - Re: Is there a reason hard links from /proc/$PID/fd/$NUM are disallowed?

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: <20111204210027.GA2203@ZenIV.linux.org.uk>
Date:	Sun, 4 Dec 2011 21:00:27 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	George Spelvin <linux@...izon.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Is there a reason hard links from /proc/$PID/fd/$NUM are
 disallowed?

On Sun, Dec 04, 2011 at 03:40:44PM -0500, George Spelvin wrote:
> I was trying to save a large file that was in mid-download that I had
> accidentally deleted (as part of making space in /tmp to hold the file!).
> 
> Since it was being held open by the download process, I tried
> 
> ln /proc/$PID/fd/$FD /tmp/bigfile.mp4

You do realize that link(2) does *NOT* follow links, do you?  linkat(2)
does, if you explicitly ask for that:

linkat(AT_FDCWD, "/proc/42/fd/1", AT_FDCWD, "/tmp/foo", AT_SYMLINK_FOLLOW)

will do it just fine.
--
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/