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, 257 insertions, 0 deletions

diff --git a/lib/test_hexdump.c b/lib/test_hexdump.c
new file mode 100644
index 000000000..751645645
--- /dev/null
+++ b/lib/test_hexdump.c
@@ -0,0 +1,257 @@
+/*
+ * Test cases for lib/hexdump.c module.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/string.h>
+
+static const unsigned char data_b[] = {
+	'\xbe', '\x32', '\xdb', '\x7b', '\x0a', '\x18', '\x93', '\xb2',	/* 00 - 07 */
+	'\x70', '\xba', '\xc4', '\x24', '\x7d', '\x83', '\x34', '\x9b',	/* 08 - 0f */
+	'\xa6', '\x9c', '\x31', '\xad', '\x9c', '\x0f', '\xac', '\xe9',	/* 10 - 17 */
+	'\x4c', '\xd1', '\x19', '\x99', '\x43', '\xb1', '\xaf', '\x0c',	/* 18 - 1f */
+};
+
+static const unsigned char data_a[] = ".2.{....p..$}.4...1.....L...C...";
+
+static const char * const test_data_1[] __initconst = {
+	"be", "32", "db", "7b", "0a", "18", "93", "b2",
+	"70", "ba", "c4", "24", "7d", "83", "34", "9b",
+	"a6", "9c", "31", "ad", "9c", "0f", "ac", "e9",
+	"4c", "d1", "19", "99", "43", "b1", "af", "0c",
+};
+
+static const char * const test_data_2_le[] __initconst = {
+	"32be", "7bdb", "180a", "b293",
+	"ba70", "24c4", "837d", "9b34",
+	"9ca6", "ad31", "0f9c", "e9ac",
+	"d14c", "9919", "b143", "0caf",
+};
+
+static const char * const test_data_2_be[] __initconst = {
+	"be32", "db7b", "0a18", "93b2",
+	"70ba", "c424", "7d83", "349b",
+	"a69c", "31ad", "9c0f", "ace9",
+	"4cd1", "1999", "43b1", "af0c",
+};
+
+static const char * const test_data_4_le[] __initconst = {
+	"7bdb32be", "b293180a", "24c4ba70", "9b34837d",
+	"ad319ca6", "e9ac0f9c", "9919d14c", "0cafb143",
+};
+
+static const char * const test_data_4_be[] __initconst = {
+	"be32db7b", "0a1893b2", "70bac424", "7d83349b",
+	"a69c31ad", "9c0face9", "4cd11999", "43b1af0c",
+};
+
+static const char * const test_data_8_le[] __initconst = {
+	"b293180a7bdb32be", "9b34837d24c4ba70",
+	"e9ac0f9cad319ca6", "0cafb1439919d14c",
+};
+
+static const char * const test_data_8_be[] __initconst = {
+	"be32db7b0a1893b2", "70bac4247d83349b",
+	"a69c31ad9c0face9", "4cd1199943b1af0c",
+};
+
+#define FILL_CHAR	'#'
+
+static unsigned total_tests __initdata;
+static unsigned failed_tests __initdata;
+
+static void __init test_hexdump_prepare_test(size_t len, int rowsize,
+					     int groupsize, char *test,
+					     size_t testlen, bool ascii)
+{
+	char *p;
+	const char * const *result;
+	size_t l = len;
+	int gs = groupsize, rs = rowsize;
+	unsigned int i;
+	const bool is_be = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
+
+	if (rs != 16 && rs != 32)
+		rs = 16;
+
+	if (l > rs)
+		l = rs;
+
+	if (!is_power_of_2(gs) || gs > 8 || (len % gs != 0))
+		gs = 1;
+
+	if (gs == 8)
+		result = is_be ? test_data_8_be : test_data_8_le;
+	else if (gs == 4)
+		result = is_be ? test_data_4_be : test_data_4_le;
+	else if (gs == 2)
+		result = is_be ? test_data_2_be : test_data_2_le;
+	else
+		result = test_data_1;
+
+	/* hex dump */
+	p = test;
+	for (i = 0; i < l / gs; i++) {
+		const char *q = *result++;
+		size_t amount = strlen(q);
+
+		memcpy(p, q, amount);
+		p += amount;
+
+		*p++ = ' ';
+	}
+	if (i)
+		p--;
+
+	/* ASCII part */
+	if (ascii) {
+		do {
+			*p++ = ' ';
+		} while (p < test + rs * 2 + rs / gs + 1);
+
+		memcpy(p, data_a, l);
+		p += l;
+	}
+
+	*p = '\0';
+}
+
+#define TEST_HEXDUMP_BUF_SIZE		(32 * 3 + 2 + 32 + 1)
+
+static void __init test_hexdump(size_t len, int rowsize, int groupsize,
+				bool ascii)
+{
+	char test[TEST_HEXDUMP_BUF_SIZE];
+	char real[TEST_HEXDUMP_BUF_SIZE];
+
+	total_tests++;
+
+	memset(real, FILL_CHAR, sizeof(real));
+	hex_dump_to_buffer(data_b, len, rowsize, groupsize, real, sizeof(real),
+			   ascii);
+
+	memset(test, FILL_CHAR, sizeof(test));
+	test_hexdump_prepare_test(len, rowsize, groupsize, test, sizeof(test),
+				  ascii);
+
+	if (memcmp(test, real, TEST_HEXDUMP_BUF_SIZE)) {
+		pr_err("Len: %zu row: %d group: %d\n", len, rowsize, groupsize);
+		pr_err("Result: '%s'\n", real);
+		pr_err("Expect: '%s'\n", test);
+		failed_tests++;
+	}
+}
+
+static void __init test_hexdump_set(int rowsize, bool ascii)
+{
+	size_t d = min_t(size_t, sizeof(data_b), rowsize);
+	size_t len = get_random_u32_inclusive(1, d);
+
+	test_hexdump(len, rowsize, 4, ascii);
+	test_hexdump(len, rowsize, 2, ascii);
+	test_hexdump(len, rowsize, 8, ascii);
+	test_hexdump(len, rowsize, 1, ascii);
+}
+
+static void __init test_hexdump_overflow(size_t buflen, size_t len,
+					 int rowsize, int groupsize,
+					 bool ascii)
+{
+	char test[TEST_HEXDUMP_BUF_SIZE];
+	char buf[TEST_HEXDUMP_BUF_SIZE];
+	int rs = rowsize, gs = groupsize;
+	int ae, he, e, f, r;
+	bool a;
+
+	total_tests++;
+
+	memset(buf, FILL_CHAR, sizeof(buf));
+
+	r = hex_dump_to_buffer(data_b, len, rs, gs, buf, buflen, ascii);
+
+	/*
+	 * Caller must provide the data length multiple of groupsize. The
+	 * calculations below are made with that assumption in mind.
+	 */
+	ae = rs * 2 /* hex */ + rs / gs /* spaces */ + 1 /* space */ + len /* ascii */;
+	he = (gs * 2 /* hex */ + 1 /* space */) * len / gs - 1 /* no trailing space */;
+
+	if (ascii)
+		e = ae;
+	else
+		e = he;
+
+	f = min_t(int, e + 1, buflen);
+	if (buflen) {
+		test_hexdump_prepare_test(len, rs, gs, test, sizeof(test), ascii);
+		test[f - 1] = '\0';
+	}
+	memset(test + f, FILL_CHAR, sizeof(test) - f);
+
+	a = r == e && !memcmp(test, buf, TEST_HEXDUMP_BUF_SIZE);
+
+	buf[sizeof(buf) - 1] = '\0';
+
+	if (!a) {
+		pr_err("Len: %zu buflen: %zu strlen: %zu\n",
+			len, buflen, strnlen(buf, sizeof(buf)));
+		pr_err("Result: %d '%s'\n", r, buf);
+		pr_err("Expect: %d '%s'\n", e, test);
+		failed_tests++;
+	}
+}
+
+static void __init test_hexdump_overflow_set(size_t buflen, bool ascii)
+{
+	unsigned int i = 0;
+	int rs = get_random_u32_inclusive(1, 2) * 16;
+
+	do {
+		int gs = 1 << i;
+		size_t len = get_random_u32_below(rs) + gs;
+
+		test_hexdump_overflow(buflen, rounddown(len, gs), rs, gs, ascii);
+	} while (i++ < 3);
+}
+
+static int __init test_hexdump_init(void)
+{
+	unsigned int i;
+	int rowsize;
+
+	rowsize = get_random_u32_inclusive(1, 2) * 16;
+	for (i = 0; i < 16; i++)
+		test_hexdump_set(rowsize, false);
+
+	rowsize = get_random_u32_inclusive(1, 2) * 16;
+	for (i = 0; i < 16; i++)
+		test_hexdump_set(rowsize, true);
+
+	for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
+		test_hexdump_overflow_set(i, false);
+
+	for (i = 0; i <= TEST_HEXDUMP_BUF_SIZE; i++)
+		test_hexdump_overflow_set(i, true);
+
+	if (failed_tests == 0)
+		pr_info("all %u tests passed\n", total_tests);
+	else
+		pr_err("failed %u out of %u tests\n", failed_tests, total_tests);
+
+	return failed_tests ? -EINVAL : 0;
+}
+module_init(test_hexdump_init);
+
+static void __exit test_hexdump_exit(void)
+{
+	/* do nothing */
+}
+module_exit(test_hexdump_exit);
+
+MODULE_AUTHOR("Andy Shevchenko <andriy.shevchenko@linux.intel.com>");
+MODULE_DESCRIPTION("Test cases for lib/hexdump.c module");
+MODULE_LICENSE("Dual BSD/GPL");