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, 162 insertions, 0 deletions

diff --git a/lib/tests/uuid_kunit.c b/lib/tests/uuid_kunit.c
new file mode 100644
index 000000000..2ef64fbe6
--- /dev/null
+++ b/lib/tests/uuid_kunit.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*
+ * Test cases for lib/uuid.c module.
+ */
+
+#include <kunit/test.h>
+#include <linux/uuid.h>
+
+struct test_uuid_data {
+	const char *uuid;
+	guid_t le;
+	uuid_t be;
+};
+
+static const struct test_uuid_data test_uuid_test_data[] = {
+	{
+		.uuid = "c33f4995-3701-450e-9fbf-206a2e98e576",
+		.le = GUID_INIT(0xc33f4995, 0x3701, 0x450e, 0x9f, 0xbf, 0x20, 0x6a, 0x2e, 0x98, 0xe5, 0x76),
+		.be = UUID_INIT(0xc33f4995, 0x3701, 0x450e, 0x9f, 0xbf, 0x20, 0x6a, 0x2e, 0x98, 0xe5, 0x76),
+	},
+	{
+		.uuid = "64b4371c-77c1-48f9-8221-29f054fc023b",
+		.le = GUID_INIT(0x64b4371c, 0x77c1, 0x48f9, 0x82, 0x21, 0x29, 0xf0, 0x54, 0xfc, 0x02, 0x3b),
+		.be = UUID_INIT(0x64b4371c, 0x77c1, 0x48f9, 0x82, 0x21, 0x29, 0xf0, 0x54, 0xfc, 0x02, 0x3b),
+	},
+	{
+		.uuid = "0cb4ddff-a545-4401-9d06-688af53e7f84",
+		.le = GUID_INIT(0x0cb4ddff, 0xa545, 0x4401, 0x9d, 0x06, 0x68, 0x8a, 0xf5, 0x3e, 0x7f, 0x84),
+		.be = UUID_INIT(0x0cb4ddff, 0xa545, 0x4401, 0x9d, 0x06, 0x68, 0x8a, 0xf5, 0x3e, 0x7f, 0x84),
+	},
+};
+
+static const char * const test_uuid_wrong_data[] = {
+	"c33f4995-3701-450e-9fbf206a2e98e576 ",	/* no hyphen(s) */
+	"64b4371c-77c1-48f9-8221-29f054XX023b",	/* invalid character(s) */
+	"0cb4ddff-a545-4401-9d06-688af53e",	/* not enough data */
+};
+
+static void uuid_test_guid_valid(struct kunit *test)
+{
+	unsigned int i;
+	const struct test_uuid_data *data;
+	guid_t le;
+
+	for (i = 0; i < ARRAY_SIZE(test_uuid_test_data); i++) {
+		data = &test_uuid_test_data[i];
+		KUNIT_EXPECT_EQ(test, guid_parse(data->uuid, &le), 0);
+		KUNIT_EXPECT_TRUE(test, guid_equal(&data->le, &le));
+	}
+}
+
+static void uuid_test_uuid_valid(struct kunit *test)
+{
+	unsigned int i;
+	const struct test_uuid_data *data;
+	uuid_t be;
+
+	for (i = 0; i < ARRAY_SIZE(test_uuid_test_data); i++) {
+		data = &test_uuid_test_data[i];
+		KUNIT_EXPECT_EQ(test, uuid_parse(data->uuid, &be), 0);
+		KUNIT_EXPECT_TRUE(test, uuid_equal(&data->be, &be));
+	}
+}
+
+static void uuid_test_guid_invalid(struct kunit *test)
+{
+	unsigned int i;
+	const char *uuid;
+	guid_t le;
+
+	for (i = 0; i < ARRAY_SIZE(test_uuid_wrong_data); i++) {
+		uuid = test_uuid_wrong_data[i];
+		KUNIT_EXPECT_EQ(test, guid_parse(uuid, &le), -EINVAL);
+	}
+}
+
+static void uuid_test_uuid_invalid(struct kunit *test)
+{
+	unsigned int i;
+	const char *uuid;
+	uuid_t be;
+
+	for (i = 0; i < ARRAY_SIZE(test_uuid_wrong_data); i++) {
+		uuid = test_uuid_wrong_data[i];
+		KUNIT_EXPECT_EQ(test, uuid_parse(uuid, &be), -EINVAL);
+	}
+}
+
+/*
+ * RFC 4122 section 4.4 says random UUIDs/GUIDs (version 4) must have:
+ *   - version 4 in the high nibble of the version byte,
+ *   - variant DCE 1.1 (binary 10x) in the high bits of byte 8.
+ *
+ * The version byte is byte 6 in the "wire" uuid_t layout and byte 7 in
+ * the byte-swapped guid_t layout.
+ */
+static void uuid_test_uuid_gen(struct kunit *test)
+{
+	uuid_t u;
+
+	for (unsigned int i = 0; i < 8; i++) {
+		uuid_gen(&u);
+		KUNIT_EXPECT_EQ(test, u.b[6] & 0xf0, 0x40);
+		KUNIT_EXPECT_EQ(test, u.b[8] & 0xc0, 0x80);
+	}
+}
+
+static void uuid_test_guid_gen(struct kunit *test)
+{
+	guid_t g;
+
+	for (unsigned int i = 0; i < 8; i++) {
+		guid_gen(&g);
+		KUNIT_EXPECT_EQ(test, g.b[7] & 0xf0, 0x40);
+		KUNIT_EXPECT_EQ(test, g.b[8] & 0xc0, 0x80);
+	}
+}
+
+static void uuid_test_generate_random_uuid(struct kunit *test)
+{
+	unsigned char buf[16];
+
+	for (unsigned int i = 0; i < 8; i++) {
+		generate_random_uuid(buf);
+		KUNIT_EXPECT_EQ(test, buf[6] & 0xf0, 0x40);
+		KUNIT_EXPECT_EQ(test, buf[8] & 0xc0, 0x80);
+	}
+}
+
+static void uuid_test_generate_random_guid(struct kunit *test)
+{
+	unsigned char buf[16];
+
+	for (unsigned int i = 0; i < 8; i++) {
+		generate_random_guid(buf);
+		KUNIT_EXPECT_EQ(test, buf[7] & 0xf0, 0x40);
+		KUNIT_EXPECT_EQ(test, buf[8] & 0xc0, 0x80);
+	}
+}
+
+static struct kunit_case uuid_test_cases[] = {
+	KUNIT_CASE(uuid_test_guid_valid),
+	KUNIT_CASE(uuid_test_uuid_valid),
+	KUNIT_CASE(uuid_test_guid_invalid),
+	KUNIT_CASE(uuid_test_uuid_invalid),
+	KUNIT_CASE(uuid_test_uuid_gen),
+	KUNIT_CASE(uuid_test_guid_gen),
+	KUNIT_CASE(uuid_test_generate_random_uuid),
+	KUNIT_CASE(uuid_test_generate_random_guid),
+	{},
+};
+
+static struct kunit_suite uuid_test_suite = {
+	.name = "uuid",
+	.test_cases = uuid_test_cases,
+};
+
+kunit_test_suite(uuid_test_suite);
+
+MODULE_AUTHOR("Andy Shevchenko <andriy.shevchenko@linux.intel.com>");
+MODULE_DESCRIPTION("Test cases for lib/uuid.c module");
+MODULE_LICENSE("Dual BSD/GPL");