thunderbolt: Fix NULL dereference in tb_remove_work()grafted

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 245 insertions, 0 deletions

diff --git a/tools/docs/documentation-file-ref-check b/tools/docs/documentation-file-ref-check
new file mode 100755
index 000000000..93b53f3a5
--- /dev/null
+++ b/tools/docs/documentation-file-ref-check
@@ -0,0 +1,245 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# Treewide grep for references to files under Documentation, and report
+# non-existing files in stderr.
+
+use warnings;
+use strict;
+use Getopt::Long qw(:config no_auto_abbrev);
+
+# NOTE: only add things here when the file was gone, but the text wants
+# to mention a past documentation file, for example, to give credits for
+# the original work.
+my %false_positives = (
+	"Documentation/scsi/scsi_mid_low_api.rst" => "Documentation/Configure.help",
+	"drivers/vhost/vhost.c" => "Documentation/virtual/lguest/lguest.c",
+);
+
+my $scriptname = $0;
+$scriptname =~ s,tools/docs/([^/]+/),$1,;
+
+# Parse arguments
+my $help = 0;
+my $fix = 0;
+my $warn = 0;
+
+if (! -e ".git") {
+	printf "Warning: can't check if file exists, as this is not a git tree\n";
+	exit 0;
+}
+
+GetOptions(
+	'fix' => \$fix,
+	'warn' => \$warn,
+	'h|help|usage' => \$help,
+);
+
+if ($help != 0) {
+    print "$scriptname [--help] [--fix]\n";
+    exit -1;
+}
+
+# Step 1: find broken references
+print "Finding broken references. This may take a while...  " if ($fix);
+
+my %broken_ref;
+
+my $doc_fix = 0;
+
+open IN, "git grep ':doc:\`' Documentation/|"
+     or die "Failed to run git grep";
+while (<IN>) {
+	next if (!m,^([^:]+):.*\:doc\:\`([^\`]+)\`,);
+	next if (m,sphinx/,);
+
+	my $file = $1;
+	my $d = $1;
+	my $doc_ref = $2;
+
+	my $f = $doc_ref;
+
+	$d =~ s,(.*/).*,$1,;
+	$f =~ s,.*\<([^\>]+)\>,$1,;
+
+	if ($f =~ m,^/,) {
+		$f = "$f.rst";
+		$f =~ s,^/,Documentation/,;
+	} else {
+		$f = "$d$f.rst";
+	}
+
+	next if (grep -e, glob("$f"));
+
+	if ($fix && !$doc_fix) {
+		print STDERR "\nWARNING: Currently, can't fix broken :doc:`` fields\n";
+	}
+	$doc_fix++;
+
+	print STDERR "$file: :doc:`$doc_ref`\n";
+}
+close IN;
+
+open IN, "git grep 'Documentation/'|"
+     or die "Failed to run git grep";
+while (<IN>) {
+	next if (!m/^([^:]+):(.*)/);
+
+	my $f = $1;
+	my $ln = $2;
+
+	# On linux-next, discard the Next/ directory
+	next if ($f =~ m,^Next/,);
+
+	# Makefiles and scripts contain nasty expressions to parse docs
+	next if ($f =~ m/Makefile/ || $f =~ m/\.(sh|py|pl|~|rej|org|orig)$/);
+
+	# It doesn't make sense to parse hidden files
+	next if ($f =~ m#/\.#);
+
+	# Skip this script
+	next if ($f eq $scriptname);
+
+	# Ignore the dir where documentation will be built
+	next if ($ln =~ m,\b(\S*)Documentation/output,);
+
+	if ($ln =~ m,\b(\S*)(Documentation/[A-Za-z0-9\_\.\,\~/\*\[\]\?+-]*)(.*),) {
+		my $prefix = $1;
+		my $ref = $2;
+		my $base = $2;
+		my $extra = $3;
+
+		# some file references are like:
+		# /usr/src/linux/Documentation/DMA-{API,mapping}.txt
+		# For now, ignore them
+		next if ($extra =~ m/^{/);
+
+		# Remove footnotes at the end like:
+		# Documentation/devicetree/dt-object-internal.txt[1]
+		$ref =~ s/(txt|rst)\[\d+]$/$1/;
+
+		# Remove ending ']' without any '['
+		$ref =~ s/\].*// if (!($ref =~ m/\[/));
+
+		# Remove puntuation marks at the end
+		$ref =~ s/[\,\.]+$//;
+
+		my $fulref = "$prefix$ref";
+
+		$fulref =~ s/^(\<file|ref)://;
+		$fulref =~ s/^[\'\`]+//;
+		$fulref =~ s,^\$\(.*\)/,,;
+		$base =~ s,.*/,,;
+
+		# Remove URL false-positives
+		next if ($fulref =~ m/^http/);
+
+		# Remove sched-pelt false-positive
+		next if ($fulref =~ m,^Documentation/scheduler/sched-pelt$,);
+
+		# Discard some build examples from Documentation/target/tcm_mod_builder.rst
+		next if ($fulref =~ m,mnt/sdb/lio-core-2.6.git/Documentation/target,);
+
+		# Check if exists, evaluating wildcards
+		next if (grep -e, glob("$ref $fulref"));
+
+		# Accept relative Documentation paths for tools/
+		if ($f =~ m/tools/) {
+			my $path = $f;
+			$path =~ s,(.*)/.*,$1,;
+			$path =~ s,testing/selftests/bpf,bpf/bpftool,;
+			next if (grep -e, glob("$path/$ref $path/../$ref $path/$fulref"));
+		}
+
+		# Discard known false-positives
+		if (defined($false_positives{$f})) {
+			next if ($false_positives{$f} eq $fulref);
+		}
+
+		if ($fix) {
+			if (!($ref =~ m/(scripts|Kconfig|Kbuild)/)) {
+				$broken_ref{$ref}++;
+			}
+		} elsif ($warn) {
+			print STDERR "Warning: $f references a file that doesn't exist: $fulref\n";
+		} else {
+			print STDERR "$f: $fulref\n";
+		}
+	}
+}
+close IN;
+
+exit 0 if (!$fix);
+
+# Step 2: Seek for file name alternatives
+print "Auto-fixing broken references. Please double-check the results\n";
+
+foreach my $ref (keys %broken_ref) {
+	my $new =$ref;
+
+	my $basedir = ".";
+	# On translations, only seek inside the translations directory
+	$basedir  = $1 if ($ref =~ m,(Documentation/translations/[^/]+),);
+
+	# get just the basename
+	$new =~ s,.*/,,;
+
+	my $f="";
+
+	# usual reason for breakage: DT file moved around
+	if ($ref =~ /devicetree/) {
+		# usual reason for breakage: DT file renamed to .yaml
+		if (!$f) {
+			my $new_ref = $ref;
+			$new_ref =~ s/\.txt$/.yaml/;
+			$f=$new_ref if (-f $new_ref);
+		}
+
+		if (!$f) {
+			my $search = $new;
+			$search =~ s,^.*/,,;
+			$f = qx(find Documentation/devicetree/ -iname "*$search*") if ($search);
+			if (!$f) {
+				# Manufacturer name may have changed
+				$search =~ s/^.*,//;
+				$f = qx(find Documentation/devicetree/ -iname "*$search*") if ($search);
+			}
+		}
+	}
+
+	# usual reason for breakage: file renamed to .rst
+	if (!$f) {
+		$new =~ s/\.txt$/.rst/;
+		$f=qx(find $basedir -iname $new) if ($new);
+	}
+
+	# usual reason for breakage: use dash or underline
+	if (!$f) {
+		$new =~ s/[-_]/[-_]/g;
+		$f=qx(find $basedir -iname $new) if ($new);
+	}
+
+	# Wild guess: seek for the same name on another place
+	if (!$f) {
+		$f = qx(find $basedir -iname $new) if ($new);
+	}
+
+	my @find = split /\s+/, $f;
+
+	if (!$f) {
+		print STDERR "ERROR: Didn't find a replacement for $ref\n";
+	} elsif (scalar(@find) > 1) {
+		print STDERR "WARNING: Won't auto-replace, as found multiple files close to $ref:\n";
+		foreach my $j (@find) {
+			$j =~ s,^./,,;
+			print STDERR "    $j\n";
+		}
+	} else {
+		$f = $find[0];
+		$f =~ s,^./,,;
+		print "INFO: Replacing $ref to $f\n";
+		foreach my $j (qx(git grep -l $ref)) {
+			qx(sed "s\@$ref\@$f\@g" -i $j);
+		}
+	}
+}