linux-kernel - [PATCH v2 8/8] scripts/leaking_addresses: add timeout on file read

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Date:   Thu,  9 Nov 2017 16:09:35 +1100
From:   "Tobin C. Harding" <me@...in.cc>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Tobin C. Harding" <me@...in.cc>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tycho Andersen <tycho@...ker.com>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        Tejun Heo <tj@...nel.org>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        Greg KH <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <wil.deacon@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: [PATCH v2 8/8] scripts/leaking_addresses: add timeout on file read

Currently script can stall if we read certain files (like
/proc/kmsg). While we have a mechanism to skip these files once they are
discovered it would be nice to not stall on as yet undiscovered files of
this kind.

Set a timer before each file is parsed, warn user if timer expires.

Suggested-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Tobin C. Harding <me@...in.cc>
---
 scripts/leaking_addresses.pl | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
index 1d6ab7f1b10c..6efd1fdb7d25 100755
--- a/scripts/leaking_addresses.pl
+++ b/scripts/leaking_addresses.pl
@@ -29,6 +29,9 @@ my $V = '0.01';
 # Directories to scan.
 my @DIRS = ('/proc', '/sys');
 
+# Timer for parsing each file, in seconds.
+my $TIMEOUT = 10;
+
 # Script can only grep for kernel addresses on the following architectures. If
 # your architecture is not listed here and has a grep'able kernel address please
 # consider submitting a patch.
@@ -284,6 +287,23 @@ sub skip_parse
 	return skip($path, \@skip_parse_files_abs, \@skip_parse_files_any);
 }
 
+sub timed_parse_file
+{
+	my ($file) = @_;
+
+	eval {
+		local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required.
+		alarm $TIMEOUT;
+		parse_file($file);
+		alarm 0;
+	};
+
+	if ($@) {
+		die unless $@ eq "alarm\n";	# Propagate unexpected errors.
+		printf STDERR "timed out parsing: %s\n", $file;
+	}
+}
+
 sub parse_file
 {
 	my ($file) = @_;
@@ -335,7 +355,7 @@ sub walk
 			if (-d $path) {
 				push @dirs, $path;
 			} else {
-				parse_file($path);
+				timed_parse_file($path);
 			}
 		}
 	}
-- 
2.7.4