[PATCH v4 4/4] thunderbolt: test: add KUnit regression tests for XDomain property parser

[Michael Bommarito]

Add three KUnit cases that exercise the defects fixed by the sibling
commits in this series by feeding crafted XDomain property blocks to
tb_property_parse_dir():

  tb_test_property_parse_u32_wrap - entry->value = 0xffffff00 and
    entry->length = 0x100 so their u32 sum 0x100000000 wraps to 0
    under the block_len guard; without the fix the subsequent
    parse_dwdata() reads attacker-directed OOB memory.

  tb_test_property_parse_recursion - two DIRECTORY entries pointing
    at each other, driving __tb_property_parse_dir() recursion;
    without the fix the kernel stack is exhausted.

  tb_test_property_parse_dir_len_underflow - a DIRECTORY entry with
    length < 4 placed near the end of the block so the non-root UUID
    kmemdup of 4 dwords from dir_offset reads OOB before the later
    content_len = dir_len - 4 underflow path is reached.

Each test asserts tb_property_parse_dir() returns NULL on the
crafted input.  With CONFIG_KASAN=y, running these on the pre-fix
kernel produces an oops inside __tb_property_parse_dir or its
callees: u32_wrap takes a page fault on the KASAN shadow lookup for
the wild ~16 GiB OOB offset; recursion trips a KASAN out-of-bounds
report in __unwind_start as the per-task kernel stack is consumed;
dir_len_underflow trips a KASAN slab-out-of-bounds report in
kmemdup_noprof reading 16 bytes past the 28-byte block.  Post-fix
they pass cleanly.

The crafted blocks are populated by writing u32 dwords directly,
matching the existing root_directory[] style used elsewhere in
this file rather than imposing a private struct overlay.

Run with:
  ./tools/testing/kunit/kunit.py run --arch=x86_64 \
    --kconfig_add CONFIG_PCI=y --kconfig_add CONFIG_NVMEM=y \
    --kconfig_add CONFIG_USB4=y --kconfig_add CONFIG_USB4_KUNIT_TEST=y \
    --kconfig_add CONFIG_KASAN=y 'thunderbolt.tb_test_property_parse_*'

Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@xxxxxxxxx>
---
 drivers/thunderbolt/test.c | 126 +++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)

diff --git a/drivers/thunderbolt/test.c b/drivers/thunderbolt/test.c
index 1f4318249c22..f41fabf15456 100644
--- a/drivers/thunderbolt/test.c
+++ b/drivers/thunderbolt/test.c
@@ -2852,7 +2852,133 @@ static void tb_test_property_copy(struct kunit *test)
 	tb_property_free_dir(src);
 }
 
+/*
+ * Reproducers for three memory-safety defects in
+ * drivers/thunderbolt/property.c reached from a crafted XDomain
+ * PROPERTIES_RESPONSE payload.  Without the fix these trip KASAN or
+ * smash the kernel stack; with the fix each returns NULL cleanly.
+ *
+ * The on-wire entry layout matches struct tb_property_entry in
+ * property.c (private to that translation unit): u32 key_hi, u32
+ * key_lo, then a packed u32 = (type << 24) | (reserved << 16) |
+ * length, then u32 value.  Each entry is 4 dwords.
+ */
+
+static void tb_test_property_parse_u32_wrap(struct kunit *test)
+{
+	/*
+	 * 0x102 dwords: enough for the entry's length field (0x100) to
+	 * pass the "entry->length > block_len" gate so the wrap check
+	 * is actually exercised.  parse_dwdata's downstream OOB read
+	 * lands ~16 GiB past the allocation regardless.
+	 */
+	u32 *block = kunit_kzalloc(test, 0x102 * sizeof(u32), GFP_KERNEL);
+	struct tb_property_dir *dir;
+
+	KUNIT_ASSERT_NOT_NULL(test, block);
+
+	block[0] = 0x55584401;	/* "UXD" v1 magic */
+	block[1] = 0x00000004;	/* Root directory length: one entry */
+
+	/*
+	 * DATA entry whose value 0xffffff00 + length 0x100 wrap to 0
+	 * in u32, passing the sum <= block_len guard even though the
+	 * real offset is far past the allocation.
+	 */
+	block[2] = 0x61616161;	/* key_hi */
+	block[3] = 0x61616161;	/* key_lo */
+	block[4] = 0x64000100;	/* type=DATA, reserved=0, length=0x100 */
+	block[5] = 0xffffff00;	/* value */
+
+	dir = tb_property_parse_dir(block, 0x102);
+	KUNIT_EXPECT_NULL(test, dir);
+	tb_property_free_dir(dir);
+}
+
+static void tb_test_property_parse_recursion(struct kunit *test)
+{
+	/*
+	 * 10 dwords: rootdir header (2) + parent DIRECTORY entry (4) +
+	 * the child entry that lives at dir_offset(2) + UUID(4) = 6,
+	 * occupying block[6..9].  Each recursive level re-reads the
+	 * same block[6..9] as its first child entry, which is itself
+	 * a DIRECTORY pointing at offset 2.
+	 */
+	u32 *block = kunit_kzalloc(test, 10 * sizeof(u32), GFP_KERNEL);
+	struct tb_property_dir *dir;
+
+	KUNIT_ASSERT_NOT_NULL(test, block);
+
+	block[0] = 0x55584401;	/* "UXD" v1 magic */
+	block[1] = 0x00000004;	/* Root directory length: one entry */
+
+	/*
+	 * DIRECTORY entry pointing at dir_offset = 2 with length = 8.
+	 * Non-root parse derives content_offset = 6, content_len = 4,
+	 * nentries = 1.  block[6..9] is read both as the parent's UUID
+	 * (kmemdup'd into dir->uuid) and as the single child entry --
+	 * which is itself a DIRECTORY pointing at offset 2, so the
+	 * recursion never terminates and the kernel stack is exhausted.
+	 */
+	block[2] = 0x61616161;	/* key_hi */
+	block[3] = 0x61616161;	/* key_lo */
+	block[4] = 0x44000008;	/* type=DIRECTORY, reserved=0, length=8 */
+	block[5] = 0x00000002;	/* value = dir_offset */
+
+	block[6] = 0x62626262;	/* doubles as UUID dword 0 / child key_hi */
+	block[7] = 0x62626262;	/* doubles as UUID dword 1 / child key_lo */
+	block[8] = 0x44000008;	/* type=DIRECTORY, reserved=0, length=8 */
+	block[9] = 0x00000002;	/* value = dir_offset (back at parent) */
+
+	dir = tb_property_parse_dir(block, 10);
+	KUNIT_EXPECT_NULL(test, dir);
+	tb_property_free_dir(dir);
+}
+
+static void tb_test_property_parse_dir_len_underflow(struct kunit *test)
+{
+	/*
+	 * Allocate exactly 7 dwords (28 bytes) so the kmalloc-32 chunk
+	 * leaves a 4-byte slab redzone tail that KASAN-Generic can flag.
+	 * With block_len = 7, dir_offset = 4, dir_len = 3, the non-root
+	 * UUID kmemdup reads 16 bytes from byte 16, so bytes 28..31 fall
+	 * in the redzone and trip a KASAN slab-out-of-bounds report on
+	 * the pre-fix kernel.  Sizing the buffer at a power of two (32,
+	 * 64, ...) puts the over-read into the slab cache tail where
+	 * KASAN's generic shadow does not flag it, and the test reduces
+	 * to the downstream content_len = dir_len - 4 underflow path
+	 * which also returns NULL.
+	 */
+	u32 *block = kunit_kzalloc(test, 7 * sizeof(u32), GFP_KERNEL);
+	struct tb_property_dir *dir;
+
+	KUNIT_ASSERT_NOT_NULL(test, block);
+
+	block[0] = 0x55584401;	/* "UXD" v1 magic */
+	block[1] = 0x00000004;	/* Root directory length: one entry */
+
+	/*
+	 * DIRECTORY entry with length = 3 pointing at dir_offset = 4.
+	 * tb_property_entry_valid() permits value(4) + length(3) <=
+	 * block_len(7).  Non-root parse begins with a kmemdup of 4
+	 * dwords from dir_offset for the UUID; that read runs past the
+	 * 28-byte allocation before the dir_len < 4 reject would fire.
+	 */
+	block[2] = 0x61616161;	/* key_hi */
+	block[3] = 0x61616161;	/* key_lo */
+	block[4] = 0x44000003;	/* type=DIRECTORY, reserved=0, length=3 */
+	block[5] = 0x00000004;	/* value = dir_offset */
+	/* block[6] is the start of the four UUID dwords; block[7..] is OOB. */
+
+	dir = tb_property_parse_dir(block, 7);
+	KUNIT_EXPECT_NULL(test, dir);
+	tb_property_free_dir(dir);
+}
+
 static struct kunit_case tb_test_cases[] = {
+	KUNIT_CASE(tb_test_property_parse_u32_wrap),
+	KUNIT_CASE(tb_test_property_parse_recursion),
+	KUNIT_CASE(tb_test_property_parse_dir_len_underflow),
 	KUNIT_CASE(tb_test_path_basic),
 	KUNIT_CASE(tb_test_path_not_connected_walk),
 	KUNIT_CASE(tb_test_path_single_hop_walk),
-- 
2.53.0