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, 275 insertions, 0 deletions

diff --git a/lib/kunit/assert.c b/lib/kunit/assert.c
new file mode 100644
index 000000000..4c751ad85
--- /dev/null
+++ b/lib/kunit/assert.c
@@ -0,0 +1,275 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Assertion and expectation serialization API.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+#include <kunit/assert.h>
+#include <kunit/test.h>
+#include <kunit/visibility.h>
+
+#include "string-stream.h"
+
+void kunit_assert_prologue(const struct kunit_loc *loc,
+			   enum kunit_assert_type type,
+			      struct string_stream *stream)
+{
+	const char *expect_or_assert = NULL;
+
+	switch (type) {
+	case KUNIT_EXPECTATION:
+		expect_or_assert = "EXPECTATION";
+		break;
+	case KUNIT_ASSERTION:
+		expect_or_assert = "ASSERTION";
+		break;
+	}
+
+	string_stream_add(stream, "%s FAILED at %s:%d\n",
+			  expect_or_assert, loc->file, loc->line);
+}
+EXPORT_SYMBOL_GPL(kunit_assert_prologue);
+
+VISIBLE_IF_KUNIT
+void kunit_assert_print_msg(const struct va_format *message,
+			    struct string_stream *stream)
+{
+	if (message->fmt)
+		string_stream_add(stream, "\n%pV", message);
+}
+
+void kunit_fail_assert_format(const struct kunit_assert *assert,
+			      const struct va_format *message,
+			      struct string_stream *stream)
+{
+	string_stream_add(stream, "%pV", message);
+}
+EXPORT_SYMBOL_GPL(kunit_fail_assert_format);
+
+void kunit_unary_assert_format(const struct kunit_assert *assert,
+			       const struct va_format *message,
+			       struct string_stream *stream)
+{
+	const struct kunit_unary_assert *unary_assert;
+
+	unary_assert = container_of(assert, struct kunit_unary_assert, assert);
+
+	if (unary_assert->expected_true)
+		string_stream_add(stream,
+				  KUNIT_SUBTEST_INDENT "Expected %s to be true, but is false\n",
+				  unary_assert->condition);
+	else
+		string_stream_add(stream,
+				  KUNIT_SUBTEST_INDENT "Expected %s to be false, but is true\n",
+				  unary_assert->condition);
+	kunit_assert_print_msg(message, stream);
+}
+EXPORT_SYMBOL_GPL(kunit_unary_assert_format);
+
+void kunit_ptr_not_err_assert_format(const struct kunit_assert *assert,
+				     const struct va_format *message,
+				     struct string_stream *stream)
+{
+	const struct kunit_ptr_not_err_assert *ptr_assert;
+
+	ptr_assert = container_of(assert, struct kunit_ptr_not_err_assert,
+				  assert);
+
+	if (!ptr_assert->value) {
+		string_stream_add(stream,
+				  KUNIT_SUBTEST_INDENT "Expected %s is not null, but is\n",
+				  ptr_assert->text);
+	} else if (IS_ERR(ptr_assert->value)) {
+		string_stream_add(stream,
+				  KUNIT_SUBTEST_INDENT "Expected %s is not error, but is: %ld\n",
+				  ptr_assert->text,
+				  PTR_ERR(ptr_assert->value));
+	}
+	kunit_assert_print_msg(message, stream);
+}
+EXPORT_SYMBOL_GPL(kunit_ptr_not_err_assert_format);
+
+/* Checks if `text` is a literal representing `value`, e.g. "5" and 5 */
+VISIBLE_IF_KUNIT bool is_literal(const char *text, long long value)
+{
+	char *buffer;
+	int len;
+	bool ret;
+
+	len = snprintf(NULL, 0, "%lld", value);
+	if (strlen(text) != len)
+		return false;
+
+	buffer = kmalloc(len+1, GFP_KERNEL);
+	if (!buffer)
+		return false;
+
+	snprintf(buffer, len+1, "%lld", value);
+	ret = strncmp(buffer, text, len) == 0;
+
+	kfree(buffer);
+
+	return ret;
+}
+
+void kunit_binary_assert_format(const struct kunit_assert *assert,
+				const struct va_format *message,
+				struct string_stream *stream)
+{
+	const struct kunit_binary_assert *binary_assert;
+
+	binary_assert = container_of(assert, struct kunit_binary_assert,
+				     assert);
+
+	string_stream_add(stream,
+			  KUNIT_SUBTEST_INDENT "Expected %s %s %s, but\n",
+			  binary_assert->text->left_text,
+			  binary_assert->text->operation,
+			  binary_assert->text->right_text);
+	if (!is_literal(binary_assert->text->left_text, binary_assert->left_value))
+		string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %lld (0x%llx)\n",
+				  binary_assert->text->left_text,
+				  binary_assert->left_value,
+				  binary_assert->left_value);
+	if (!is_literal(binary_assert->text->right_text, binary_assert->right_value))
+		string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %lld (0x%llx)",
+				  binary_assert->text->right_text,
+				  binary_assert->right_value,
+				  binary_assert->right_value);
+	kunit_assert_print_msg(message, stream);
+}
+EXPORT_SYMBOL_GPL(kunit_binary_assert_format);
+
+void kunit_binary_ptr_assert_format(const struct kunit_assert *assert,
+				    const struct va_format *message,
+				    struct string_stream *stream)
+{
+	const struct kunit_binary_ptr_assert *binary_assert;
+
+	binary_assert = container_of(assert, struct kunit_binary_ptr_assert,
+				     assert);
+
+	string_stream_add(stream,
+			  KUNIT_SUBTEST_INDENT "Expected %s %s %s, but\n",
+			  binary_assert->text->left_text,
+			  binary_assert->text->operation,
+			  binary_assert->text->right_text);
+	string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %px\n",
+			  binary_assert->text->left_text,
+			  binary_assert->left_value);
+	string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == %px",
+			  binary_assert->text->right_text,
+			  binary_assert->right_value);
+	kunit_assert_print_msg(message, stream);
+}
+EXPORT_SYMBOL_GPL(kunit_binary_ptr_assert_format);
+
+/* Checks if KUNIT_EXPECT_STREQ() args were string literals.
+ * Note: `text` will have ""s where as `value` will not.
+ */
+VISIBLE_IF_KUNIT bool is_str_literal(const char *text, const char *value)
+{
+	int len;
+
+	len = strlen(text);
+	if (len < 2)
+		return false;
+	if (text[0] != '\"' || text[len - 1] != '\"')
+		return false;
+
+	return strncmp(text + 1, value, len - 2) == 0;
+}
+
+void kunit_binary_str_assert_format(const struct kunit_assert *assert,
+				    const struct va_format *message,
+				    struct string_stream *stream)
+{
+	const struct kunit_binary_str_assert *binary_assert;
+
+	binary_assert = container_of(assert, struct kunit_binary_str_assert,
+				     assert);
+
+	string_stream_add(stream,
+			  KUNIT_SUBTEST_INDENT "Expected %s %s %s, but\n",
+			  binary_assert->text->left_text,
+			  binary_assert->text->operation,
+			  binary_assert->text->right_text);
+	if (!is_str_literal(binary_assert->text->left_text, binary_assert->left_value))
+		string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == \"%s\"\n",
+				  binary_assert->text->left_text,
+				  binary_assert->left_value);
+	if (!is_str_literal(binary_assert->text->right_text, binary_assert->right_value))
+		string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s == \"%s\"",
+				  binary_assert->text->right_text,
+				  binary_assert->right_value);
+	kunit_assert_print_msg(message, stream);
+}
+EXPORT_SYMBOL_GPL(kunit_binary_str_assert_format);
+
+/* Adds a hexdump of a buffer to a string_stream comparing it with
+ * a second buffer. The different bytes are marked with <>.
+ */
+VISIBLE_IF_KUNIT
+void kunit_assert_hexdump(struct string_stream *stream,
+			  const void *buf,
+			  const void *compared_buf,
+			  const size_t len)
+{
+	size_t i;
+	const u8 *buf1 = buf;
+	const u8 *buf2 = compared_buf;
+
+	string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT);
+
+	for (i = 0; i < len; ++i) {
+		if (!(i % 16) && i)
+			string_stream_add(stream, "\n" KUNIT_SUBSUBTEST_INDENT);
+
+		if (buf1[i] != buf2[i])
+			string_stream_add(stream, "<%02x>", buf1[i]);
+		else
+			string_stream_add(stream, " %02x ", buf1[i]);
+	}
+}
+
+void kunit_mem_assert_format(const struct kunit_assert *assert,
+			     const struct va_format *message,
+			     struct string_stream *stream)
+{
+	const struct kunit_mem_assert *mem_assert;
+
+	mem_assert = container_of(assert, struct kunit_mem_assert,
+				  assert);
+
+	if (!mem_assert->left_value) {
+		string_stream_add(stream,
+				  KUNIT_SUBTEST_INDENT "Expected %s is not null, but is\n",
+				  mem_assert->text->left_text);
+	} else if (!mem_assert->right_value) {
+		string_stream_add(stream,
+				  KUNIT_SUBTEST_INDENT "Expected %s is not null, but is\n",
+				  mem_assert->text->right_text);
+	} else {
+		string_stream_add(stream,
+				KUNIT_SUBTEST_INDENT "Expected %s %s %s, but\n",
+				mem_assert->text->left_text,
+				mem_assert->text->operation,
+				mem_assert->text->right_text);
+
+		string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s ==\n",
+				mem_assert->text->left_text);
+		kunit_assert_hexdump(stream, mem_assert->left_value,
+					mem_assert->right_value, mem_assert->size);
+
+		string_stream_add(stream, "\n");
+
+		string_stream_add(stream, KUNIT_SUBSUBTEST_INDENT "%s ==\n",
+				mem_assert->text->right_text);
+		kunit_assert_hexdump(stream, mem_assert->right_value,
+					mem_assert->left_value, mem_assert->size);
+
+		kunit_assert_print_msg(message, stream);
+	}
+}
+EXPORT_SYMBOL_GPL(kunit_mem_assert_format);