Date: Tue, 20 Feb 2001 06:10:05 -0800 (PST) From: David Malone <dwmalone@maths.tcd.ie> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/25206: Kernel Panic Message-ID: <200102201410.f1KEA5948150@freefall.freebsd.org>
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The following reply was made to PR kern/25206; it has been noted by GNATS.
From: David Malone <dwmalone@maths.tcd.ie>
To: mm@omnix.net
Cc: freebsd-gnats-submit@FreeBSD.org, peter@FreeBSD.org,
iedowse@maths.tcd.ie
Subject: Re: kern/25206: Kernel Panic
Date: Tue, 20 Feb 2001 14:03:29 +0000
On Mon, Feb 19, 2001 at 11:34:40AM -0800, mm@omnix.net wrote:
> luser@PAF$ tail -f /dev/ttyp1
>
> now ruser is going to connect to my box:
> ruser@NOWHERE$ telnet PAF
> Connection closed by foreign host.
This seems to be caused by kqueue trying to work on a revoked file
discriptor. I think this bug is inaccessable in more recent versions
of -stable after Peter's commit to vfs_vnops.c on 2001/02/09. The
offending code looks like:
static int
filt_vnread(struct knote *kn, long hint)
{
struct vnode *vp = (struct vnode *)kn->kn_fp->f_data;
struct inode *ip = VTOI(vp);
kn->kn_data = ip->i_size - kn->kn_fp->f_offset;
return (kn->kn_data != 0);
}
There is now a check to make sure that the file is in a UFS filesystem
at the time the filter is attached. However, if the file is revoked
it could change type, so checking something like:
if (vp->v_tag != VT_UFS)
return 1;
might be a good idea. (Currently only device files can be revoked,
but that's only 'cos it was disabeled on other file types 'cos it
didn't work on fifos).
David.
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