Subject: Re: kern/950: bad "mount" arguments cause panic
To: None <firstname.lastname@example.org>
From: Chris G Demetriou <Chris_G_Demetriou@LAGAVULIN.PDL.CS.CMU.EDU>
Date: 04/10/1995 18:48:53
> The problem has shown up after a mistake giving the arguments to
> "mount". The first parts of source and target were identical:
> mount zelnfs/... zelnfs (Should be a nfs mount...)
> This causes: "panic: locking against myself".
i found this a while ago, i think more than a year ago.
> mkdir xxx
> mount xxx xxx
cute, eh? 8-)
> One more parameter check?
Unfortunately, it's _not_ that easy.
in fact, what happens is that the mount code does a namei() on the
"device node" argument and on the "mount point" argument, and in the
process manages to try to "lock against itself."
The same bug exists in SunOS (4.1.?), ULTRIX (4.2, i think), and a
bunch of other systems, though on at least the former, it simply hangs
the system, rather than panic'ing. (i was surprised to note that it
_doesn't_ happen on DEC OSF/1, now a.k.a. DEC UNIX).
The fix is non-trivial, but i'm aware of people who are working on
things which are leading in the right direction. 8-)