linux-kernel - Re: [PATCH 1/3] leaking_addresses: skip all /proc/PID except /proc/1

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: <20180227050931.4h64hkxglv3ekzsp@cisco>
Date:   Mon, 26 Feb 2018 22:09:31 -0700
From:   Tycho Andersen <tycho@...ho.ws>
To:     "Tobin C. Harding" <me@...in.cc>
Cc:     Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] leaking_addresses: skip all /proc/PID except /proc/1

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@...in.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.

Cheers,

Tycho