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![Tobin C. Harding](/assets/img/avatar_default.png)
Sometimes files may be created by using output from printk. As the scan traverses the directory tree we should parse each path name and check if it is leaking an address. Add check for leaking address on each path name. Suggested-by: Tycho Andersen <tycho@tycho.ws> Acked-by: Tycho Andersen <tycho@tycho.ws> Signed-off-by: Tobin C. Harding <me@tobin.cc>
647 lines
13 KiB
Perl
Executable file
647 lines
13 KiB
Perl
Executable file
#!/usr/bin/env perl
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#
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# (c) 2017 Tobin C. Harding <me@tobin.cc>
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# Licensed under the terms of the GNU GPL License version 2
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#
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# leaking_addresses.pl: Scan the kernel for potential leaking addresses.
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# - Scans dmesg output.
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# - Walks directory tree and parses each file (for each directory in @DIRS).
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#
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# Use --debug to output path before parsing, this is useful to find files that
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# cause the script to choke.
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#
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# When the system is idle it is likely that most files under /proc/PID will be
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# identical for various processes. Scanning _all_ the PIDs under /proc is
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# unnecessary and implies that we are thoroughly scanning /proc. This is _not_
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# the case because there may be ways userspace can trigger creation of /proc
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# files that leak addresses but were not present during a scan. For these two
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# reasons we exclude all PID directories under /proc except '1/'
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use warnings;
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use strict;
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use POSIX;
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use File::Basename;
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use File::Spec;
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use Cwd 'abs_path';
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use Term::ANSIColor qw(:constants);
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use Getopt::Long qw(:config no_auto_abbrev);
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use Config;
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use bigint qw/hex/;
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use feature 'state';
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my $P = $0;
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# Directories to scan.
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my @DIRS = ('/proc', '/sys');
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# Timer for parsing each file, in seconds.
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my $TIMEOUT = 10;
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# Kernel addresses vary by architecture. We can only auto-detect the following
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# architectures (using `uname -m`). (flag --32-bit overrides auto-detection.)
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my @SUPPORTED_ARCHITECTURES = ('x86_64', 'ppc64', 'x86');
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# Command line options.
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my $help = 0;
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my $debug = 0;
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my $raw = 0;
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my $output_raw = ""; # Write raw results to file.
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my $input_raw = ""; # Read raw results from file instead of scanning.
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my $suppress_dmesg = 0; # Don't show dmesg in output.
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my $squash_by_path = 0; # Summary report grouped by absolute path.
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my $squash_by_filename = 0; # Summary report grouped by filename.
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my $kernel_config_file = ""; # Kernel configuration file.
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my $opt_32bit = 0; # Scan 32-bit kernel.
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my $page_offset_32bit = 0; # Page offset for 32-bit kernel.
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# Skip these absolute paths.
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my @skip_abs = (
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'/proc/kmsg',
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'/proc/device-tree',
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'/proc/1/syscall',
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'/sys/firmware/devicetree',
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'/sys/kernel/debug/tracing/trace_pipe',
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'/sys/kernel/security/apparmor/revision');
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# Skip these under any subdirectory.
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my @skip_any = (
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'pagemap',
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'events',
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'access',
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'registers',
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'snapshot_raw',
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'trace_pipe_raw',
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'ptmx',
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'trace_pipe',
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'fd',
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'usbmon');
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sub help
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{
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my ($exitcode) = @_;
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print << "EOM";
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Usage: $P [OPTIONS]
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Options:
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-o, --output-raw=<file> Save results for future processing.
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-i, --input-raw=<file> Read results from file instead of scanning.
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--raw Show raw results (default).
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--suppress-dmesg Do not show dmesg results.
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--squash-by-path Show one result per unique path.
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--squash-by-filename Show one result per unique filename.
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--kernel-config-file=<file> Kernel configuration file (e.g /boot/config)
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--32-bit Scan 32-bit kernel.
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--page-offset-32-bit=o Page offset (for 32-bit kernel 0xABCD1234).
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-d, --debug Display debugging output.
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-h, --help, --version Display this help and exit.
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Scans the running kernel for potential leaking addresses.
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EOM
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exit($exitcode);
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}
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GetOptions(
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'd|debug' => \$debug,
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'h|help' => \$help,
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'version' => \$help,
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'o|output-raw=s' => \$output_raw,
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'i|input-raw=s' => \$input_raw,
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'suppress-dmesg' => \$suppress_dmesg,
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'squash-by-path' => \$squash_by_path,
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'squash-by-filename' => \$squash_by_filename,
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'raw' => \$raw,
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'kernel-config-file=s' => \$kernel_config_file,
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'32-bit' => \$opt_32bit,
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'page-offset-32-bit=o' => \$page_offset_32bit,
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) or help(1);
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help(0) if ($help);
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if ($input_raw) {
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format_output($input_raw);
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exit(0);
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}
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if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
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printf "\nSummary reporting only available with --input-raw=<file>\n";
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printf "(First run scan with --output-raw=<file>.)\n";
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exit(128);
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}
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if (!(is_supported_architecture() or $opt_32bit or $page_offset_32bit)) {
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printf "\nScript does not support your architecture, sorry.\n";
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printf "\nCurrently we support: \n\n";
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foreach(@SUPPORTED_ARCHITECTURES) {
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printf "\t%s\n", $_;
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}
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printf("\n");
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printf("If you are running a 32-bit architecture you may use:\n");
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printf("\n\t--32-bit or --page-offset-32-bit=<page offset>\n\n");
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my $archname = `uname -m`;
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printf("Machine hardware name (`uname -m`): %s\n", $archname);
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exit(129);
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}
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if ($output_raw) {
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open my $fh, '>', $output_raw or die "$0: $output_raw: $!\n";
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select $fh;
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}
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parse_dmesg();
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walk(@DIRS);
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exit 0;
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sub dprint
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{
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printf(STDERR @_) if $debug;
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}
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sub is_supported_architecture
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{
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return (is_x86_64() or is_ppc64() or is_ix86_32());
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}
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sub is_32bit
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{
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# Allow --32-bit or --page-offset-32-bit to override
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if ($opt_32bit or $page_offset_32bit) {
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return 1;
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}
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return is_ix86_32();
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}
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sub is_ix86_32
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{
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state $arch = `uname -m`;
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chomp $arch;
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if ($arch =~ m/i[3456]86/) {
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return 1;
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}
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return 0;
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}
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sub is_arch
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{
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my ($desc) = @_;
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my $arch = `uname -m`;
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chomp $arch;
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if ($arch eq $desc) {
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return 1;
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}
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return 0;
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}
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sub is_x86_64
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{
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state $is = is_arch('x86_64');
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return $is;
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}
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sub is_ppc64
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{
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state $is = is_arch('ppc64');
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return $is;
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}
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# Gets config option value from kernel config file.
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# Returns "" on error or if config option not found.
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sub get_kernel_config_option
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{
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my ($option) = @_;
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my $value = "";
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my $tmp_file = "";
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my @config_files;
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# Allow --kernel-config-file to override.
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if ($kernel_config_file ne "") {
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@config_files = ($kernel_config_file);
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} elsif (-R "/proc/config.gz") {
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my $tmp_file = "/tmp/tmpkconf";
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if (system("gunzip < /proc/config.gz > $tmp_file")) {
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dprint "$0: system(gunzip < /proc/config.gz) failed\n";
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return "";
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} else {
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@config_files = ($tmp_file);
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}
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} else {
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my $file = '/boot/config-' . `uname -r`;
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chomp $file;
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@config_files = ($file, '/boot/config');
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}
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foreach my $file (@config_files) {
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dprint("parsing config file: %s\n", $file);
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$value = option_from_file($option, $file);
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if ($value ne "") {
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last;
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}
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}
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if ($tmp_file ne "") {
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system("rm -f $tmp_file");
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}
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return $value;
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}
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# Parses $file and returns kernel configuration option value.
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sub option_from_file
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{
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my ($option, $file) = @_;
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my $str = "";
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my $val = "";
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open(my $fh, "<", $file) or return "";
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while (my $line = <$fh> ) {
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if ($line =~ /^$option/) {
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($str, $val) = split /=/, $line;
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chomp $val;
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last;
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}
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}
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close $fh;
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return $val;
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}
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sub is_false_positive
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{
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my ($match) = @_;
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if (is_32bit()) {
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return is_false_positive_32bit($match);
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}
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# 64 bit false positives.
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if ($match =~ '\b(0x)?(f|F){16}\b' or
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$match =~ '\b(0x)?0{16}\b') {
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return 1;
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}
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if (is_x86_64() and is_in_vsyscall_memory_region($match)) {
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return 1;
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}
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return 0;
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}
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sub is_false_positive_32bit
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{
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my ($match) = @_;
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state $page_offset = get_page_offset();
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if ($match =~ '\b(0x)?(f|F){8}\b') {
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return 1;
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}
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if (hex($match) < $page_offset) {
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return 1;
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}
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return 0;
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}
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# returns integer value
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sub get_page_offset
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{
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my $page_offset;
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my $default_offset = 0xc0000000;
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# Allow --page-offset-32bit to override.
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if ($page_offset_32bit != 0) {
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return $page_offset_32bit;
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}
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$page_offset = get_kernel_config_option('CONFIG_PAGE_OFFSET');
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if (!$page_offset) {
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return $default_offset;
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}
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return $page_offset;
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}
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sub is_in_vsyscall_memory_region
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{
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my ($match) = @_;
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my $hex = hex($match);
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my $region_min = hex("0xffffffffff600000");
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my $region_max = hex("0xffffffffff601000");
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return ($hex >= $region_min and $hex <= $region_max);
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}
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# True if argument potentially contains a kernel address.
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sub may_leak_address
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{
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my ($line) = @_;
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my $address_re;
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# Signal masks.
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if ($line =~ '^SigBlk:' or
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$line =~ '^SigIgn:' or
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$line =~ '^SigCgt:') {
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return 0;
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}
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if ($line =~ '\bKEY=[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b' or
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$line =~ '\b[[:xdigit:]]{14} [[:xdigit:]]{16} [[:xdigit:]]{16}\b') {
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return 0;
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}
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$address_re = get_address_re();
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while ($line =~ /($address_re)/g) {
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if (!is_false_positive($1)) {
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return 1;
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}
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}
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return 0;
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}
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sub get_address_re
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{
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if (is_ppc64()) {
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return '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
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} elsif (is_32bit()) {
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return '\b(0x)?[[:xdigit:]]{8}\b';
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}
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return get_x86_64_re();
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}
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sub get_x86_64_re
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{
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# We handle page table levels but only if explicitly configured using
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# CONFIG_PGTABLE_LEVELS. If config file parsing fails or config option
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# is not found we default to using address regular expression suitable
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# for 4 page table levels.
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state $ptl = get_kernel_config_option('CONFIG_PGTABLE_LEVELS');
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if ($ptl == 5) {
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return '\b(0x)?ff[[:xdigit:]]{14}\b';
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}
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return '\b(0x)?ffff[[:xdigit:]]{12}\b';
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}
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sub parse_dmesg
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{
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open my $cmd, '-|', 'dmesg';
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while (<$cmd>) {
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if (may_leak_address($_)) {
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print 'dmesg: ' . $_;
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}
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}
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close $cmd;
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}
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# True if we should skip this path.
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sub skip
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{
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my ($path) = @_;
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foreach (@skip_abs) {
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return 1 if (/^$path$/);
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}
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my($filename, $dirs, $suffix) = fileparse($path);
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foreach (@skip_any) {
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return 1 if (/^$filename$/);
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}
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return 0;
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}
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sub timed_parse_file
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{
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my ($file) = @_;
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eval {
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local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required.
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alarm $TIMEOUT;
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parse_file($file);
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alarm 0;
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};
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if ($@) {
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die unless $@ eq "alarm\n"; # Propagate unexpected errors.
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printf STDERR "timed out parsing: %s\n", $file;
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}
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}
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sub parse_file
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{
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my ($file) = @_;
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if (! -R $file) {
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return;
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}
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if (! -T $file) {
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return;
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}
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open my $fh, "<", $file or return;
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while ( <$fh> ) {
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if (may_leak_address($_)) {
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print $file . ': ' . $_;
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}
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}
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close $fh;
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}
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# Checks if the actual path name is leaking a kernel address.
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sub check_path_for_leaks
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{
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my ($path) = @_;
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if (may_leak_address($path)) {
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printf("Path name may contain address: $path\n");
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}
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}
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# Recursively walk directory tree.
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sub walk
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{
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my @dirs = @_;
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while (my $pwd = shift @dirs) {
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next if (!opendir(DIR, $pwd));
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my @files = readdir(DIR);
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closedir(DIR);
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foreach my $file (@files) {
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next if ($file eq '.' or $file eq '..');
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my $path = "$pwd/$file";
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next if (-l $path);
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# skip /proc/PID except /proc/1
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next if (($path =~ /^\/proc\/[0-9]+$/) &&
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($path !~ /^\/proc\/1$/));
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next if (skip($path));
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check_path_for_leaks($path);
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if (-d $path) {
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push @dirs, $path;
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next;
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}
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dprint "parsing: $path\n";
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timed_parse_file($path);
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}
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}
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}
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sub format_output
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{
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my ($file) = @_;
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# Default is to show raw results.
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if ($raw or (!$squash_by_path and !$squash_by_filename)) {
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dump_raw_output($file);
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return;
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}
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my ($total, $dmesg, $paths, $files) = parse_raw_file($file);
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printf "\nTotal number of results from scan (incl dmesg): %d\n", $total;
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if (!$suppress_dmesg) {
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print_dmesg($dmesg);
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}
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if ($squash_by_filename) {
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squash_by($files, 'filename');
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}
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if ($squash_by_path) {
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squash_by($paths, 'path');
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}
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}
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sub dump_raw_output
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{
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my ($file) = @_;
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open (my $fh, '<', $file) or die "$0: $file: $!\n";
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while (<$fh>) {
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if ($suppress_dmesg) {
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if ("dmesg:" eq substr($_, 0, 6)) {
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next;
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}
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}
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print $_;
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}
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close $fh;
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}
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sub parse_raw_file
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{
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my ($file) = @_;
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my $total = 0; # Total number of lines parsed.
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my @dmesg; # dmesg output.
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my %files; # Unique filenames containing leaks.
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my %paths; # Unique paths containing leaks.
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open (my $fh, '<', $file) or die "$0: $file: $!\n";
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while (my $line = <$fh>) {
|
|
$total++;
|
|
|
|
if ("dmesg:" eq substr($line, 0, 6)) {
|
|
push @dmesg, $line;
|
|
next;
|
|
}
|
|
|
|
cache_path(\%paths, $line);
|
|
cache_filename(\%files, $line);
|
|
}
|
|
|
|
return $total, \@dmesg, \%paths, \%files;
|
|
}
|
|
|
|
sub print_dmesg
|
|
{
|
|
my ($dmesg) = @_;
|
|
|
|
print "\ndmesg output:\n";
|
|
|
|
if (@$dmesg == 0) {
|
|
print "<no results>\n";
|
|
return;
|
|
}
|
|
|
|
foreach(@$dmesg) {
|
|
my $index = index($_, ': ');
|
|
$index += 2; # skid ': '
|
|
print substr($_, $index);
|
|
}
|
|
}
|
|
|
|
sub squash_by
|
|
{
|
|
my ($ref, $desc) = @_;
|
|
|
|
print "\nResults squashed by $desc (excl dmesg). ";
|
|
print "Displaying [<number of results> <$desc>], <example result>\n";
|
|
|
|
if (keys %$ref == 0) {
|
|
print "<no results>\n";
|
|
return;
|
|
}
|
|
|
|
foreach(keys %$ref) {
|
|
my $lines = $ref->{$_};
|
|
my $length = @$lines;
|
|
printf "[%d %s] %s", $length, $_, @$lines[0];
|
|
}
|
|
}
|
|
|
|
sub cache_path
|
|
{
|
|
my ($paths, $line) = @_;
|
|
|
|
my $index = index($line, ': ');
|
|
my $path = substr($line, 0, $index);
|
|
|
|
$index += 2; # skip ': '
|
|
add_to_cache($paths, $path, substr($line, $index));
|
|
}
|
|
|
|
sub cache_filename
|
|
{
|
|
my ($files, $line) = @_;
|
|
|
|
my $index = index($line, ': ');
|
|
my $path = substr($line, 0, $index);
|
|
my $filename = basename($path);
|
|
|
|
$index += 2; # skip ': '
|
|
add_to_cache($files, $filename, substr($line, $index));
|
|
}
|
|
|
|
sub add_to_cache
|
|
{
|
|
my ($cache, $key, $value) = @_;
|
|
|
|
if (!$cache->{$key}) {
|
|
$cache->{$key} = ();
|
|
}
|
|
push @{$cache->{$key}}, $value;
|
|
}
|