From: "Tobin C. Harding" <me@tobin.cc>
To: Tycho Andersen <tycho@tycho.ws>
Cc: Kernel Hardening <kernel-hardening@lists.openwall.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/3] leaking_addresses: skip all /proc/PID except /proc/1
Date: Tue, 27 Feb 2018 17:29:50 +1100 [thread overview]
Message-ID: <20180227062950.GK15131@eros> (raw)
In-Reply-To: <20180227050931.4h64hkxglv3ekzsp@cisco>
On Mon, Feb 26, 2018 at 10:09:31PM -0700, Tycho Andersen wrote:
> Hi Tobin,
>
> On Tue, Feb 27, 2018 at 03:45:09PM +1100, Tobin C. Harding wrote:
> > When the system is idle it is likely that most files under /proc/PID
> > will be identical for various processes. Scanning _all_ the PIDs under
> > /proc is unnecessary and implies that we are thoroughly scanning /proc.
> > This is _not_ the case because there may be ways userspace can trigger
> > creation of /proc files that leak addresses but were not present during
> > a scan. For these two reasons we should exclude all PID directories
> > under /proc except '1/'
> >
> > Exclude all /proc/PID except /proc/1.
> >
> > Signed-off-by: Tobin C. Harding <me@tobin.cc>
> > ---
> > scripts/leaking_addresses.pl | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> > index 6e5bc57caeaa..fb40e2828f43 100755
> > --- a/scripts/leaking_addresses.pl
> > +++ b/scripts/leaking_addresses.pl
> > @@ -10,6 +10,14 @@
> > # Use --debug to output path before parsing, this is useful to find files that
> > # cause the script to choke.
> >
> > +#
> > +# When the system is idle it is likely that most files under /proc/PID will be
> > +# identical for various processes. Scanning _all_ the PIDs under /proc is
> > +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_
> > +# the case because there may be ways userspace can trigger creation of /proc
> > +# files that leak addresses but were not present during a scan. For these two
> > +# reasons we exclude all PID directories under /proc except '1/'
> > +
> > use warnings;
> > use strict;
> > use POSIX;
> > @@ -472,6 +480,9 @@ sub walk
> > my $path = "$pwd/$file";
> > next if (-l $path);
> >
> > + # skip /proc/PID except /proc/1
> > + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/);
>
> Can't we just do,
>
> substr($path, 0, len("/proc/1/")) eq "/proc/1/" ?
>
> seems much easier to read than the regex.
This is much better. I guess it's true what they say, be careful after
reading a book about hammers, everything will look like a nail.
Tobin
next prev parent reply other threads:[~2018-02-27 6:29 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-27 4:45 [PATCH 0/3] leaking_addresses: limit scan to PID==1 Tobin C. Harding
2018-02-27 4:45 ` [PATCH 1/3] leaking_addresses: skip all /proc/PID except /proc/1 Tobin C. Harding
2018-02-27 5:09 ` Tycho Andersen
2018-02-27 6:29 ` Tobin C. Harding [this message]
2018-02-27 7:15 ` Alexander Kapshuk
2018-02-27 21:06 ` Tobin C. Harding
2018-03-01 21:06 ` Tobin C. Harding
2018-03-01 22:46 ` Tycho Andersen
2018-03-03 9:44 ` Alexander Kapshuk
2018-02-27 4:45 ` [PATCH 2/3] leaking_addresses: skip '/proc/1/syscall' Tobin C. Harding
2018-02-27 4:45 ` [PATCH 3/3] leaking_addresses: remove version number Tobin C. Harding
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180227062950.GK15131@eros \
--to=me@tobin.cc \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-kernel@vger.kernel.org \
--cc=tycho@tycho.ws \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).