linux-kernel - since when does linkat() on deleted /proc/$PID/fd/$num return ENOENT ?

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-next>] [day] [month] [year] [list]

Message-ID: <20120330102121.GA5999@aldebaran.gro-tsen.net>
Date:	Fri, 30 Mar 2012 12:21:21 +0200
From:	David Madore <david+ml@...ore.org>
To:	Linux Kernel Mailing-List <linux-kernel@...r.kernel.org>
Subject: since when does linkat() on deleted /proc/$PID/fd/$num return
 ENOENT ?

It used to be the case (last time I checked was around late 2008 or
early 2009) that deleted entries from /proc/$PID/fd/ could be linked
back to the filesystem by using linkat(,,,,AT_SYMLINK_FOLLOW).

Now this just returns ENOENT.

I'd like to understand when, how and why this change took place.  What
commit introduced it and was it a deliberate move (e.g., because the
feature was a security issue of itself, or came into conflict with
something else) or was it accidental?  Does it depend on the /proc
filesystem itself or on the target filesystem where the deleted file
used to reside?

(There's a Reddit thread, <URL:
http://www.reddit.com/r/programming/comments/7yx6f/how_to_undelete_any_open_deleted_file_in_linux/
 >, where some people are reporting ENOENT on 2.6.27 or perhaps even
2.6.26, which helps but a bound on the change.)

(See also this thread: <URL:
http://comments.gmane.org/gmane.linux.kernel/1224071
 >, where the question is not answered, however.)

-- 
     David A. Madore
   ( http://www.madore.org/~david/ )
--
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/