[PATCH 2/2] thunderbolt: test: add KUnit regression tests for XDomain property parser

Michael Bommarito
2026-04-15T03:23:54Z

Add three KUnit cases that exercise the defects fixed by the parent
commit 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 so non-root content_len = dir_len - 4 wraps size_t;
without the fix nentries is huge and the entry walk runs OOB.

Each test asserts tb_property_parse_dir() returns NULL on the
crafted input. With CONFIG_KASAN=y, running these on the pre-fix
kernel reproduces an oops inside __tb_property_parse_dir (KASAN
shadow-memory fault for the u32_wrap case, stack-guard trip for
recursion, OOB read past block for dir_len underflow). Post-fix
they pass cleanly.

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-4-6
Assisted-by: Codex:gpt-5-4
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
drivers/thunderbolt/test.c | 127 +++++++++++++++++++++++++++++++++++++
1 file changed, 127 insertions(+)

diff --git a/drivers/thunderbolt/test.c b/drivers/thunderbolt/test.c
index 1f4318249c22..22f4107fcb8d 100644
--- a/drivers/thunderbolt/test.c
+++ b/drivers/thunderbolt/test.c
@@ -2852,7 +2852,134 @@ 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.
+ */
+static void tb_test_property_parse_u32_wrap(struct kunit *test)
+{
+ u32 *block = kunit_kzalloc(test, 500 * sizeof(u32), GFP_KERNEL);
+ struct tb_property_dir *dir;
+ struct {
+ u32 key_hi, key_lo;
+ u16 length;
+ u8 reserved;
+ u8 type;
+ u32 value;
+ } *e;
+
+ /* Root header: magic + length=6 (single entry body of 4 dwords +
+ * 2 slack, keeps walk within block[]). */
+ block[0] = 0x55584401;
+ block[1] = 6;
+
+ /* Crafted DATA entry at block[2..5]: value = 0xFFFFFF00 and
+ * length = 0x100 are u32/u16 such that the u32 sum 0x100000000
+ * wraps to 0, passing the sum <= block_len guard even though
+ * the real offset is block + 0xFFFFFF00 * 4 (~16 GiB past the
+ * block). The subsequent parse_dwdata() at property.c:132
+ * copies entry->length*4 = 1024 bytes from that wild address
+ * into a fresh kcalloc buffer.
+ */
+ e = (void *)&block[2];
+ e->key_hi = 0x61616161;
+ e->key_lo = 0x61616161;
+ e->length = 0x100;
+ e->type = 0x64; /* TB_PROPERTY_TYPE_DATA */
+ e->value = 0xFFFFFF00;
+
+ dir = tb_property_parse_dir(block, 500);
+ /* With the fix this returns NULL; without it, KASAN splats in
+ * be32_to_cpu_array() / memcpy reading block + value*4 out of
+ * bounds. Assert on the safe outcome: a NULL dir. */
+ KUNIT_EXPECT_NULL(test, dir);
+ tb_property_free_dir(dir);
+}
+
+static void tb_test_property_parse_recursion(struct kunit *test)
+{
+ u32 *block = kunit_kzalloc(test, 500 * sizeof(u32), GFP_KERNEL);
+ struct tb_property_dir *dir;
+ struct entry {
+ u32 key_hi, key_lo;
+ u16 length;
+ u8 reserved;
+ u8 type;
+ u32 value;
+ } *e, *child_e;
+
+ block[0] = 0x55584401;
+ block[1] = 4; /* rootdir length = one entry */
+
+ /* DIRECTORY entry pointing at dir_offset=2 with length=16.
+ * When parsed as non-root: content_offset = 6, content_len = 12,
+ * nentries = 3. The child's first entry at block[6] is also
+ * DIRECTORY pointing at 2, so the recursion oscillates between
+ * two dir_offsets until the kernel stack is exhausted.
+ */
+ e = (void *)&block[2];
+ e->key_hi = 0x61616161;
+ e->key_lo = 0x61616161;
+ e->length = 16;
+ e->type = 0x44; /* TB_PROPERTY_TYPE_DIRECTORY */
+ e->value = 2;
+
+ child_e = (void *)&block[6];
+ child_e->key_hi = 0x62626262;
+ child_e->key_lo = 0x62626262;
+ child_e->length = 16;
+ child_e->type = 0x44;
+ child_e->value = 2;
+
+ dir = tb_property_parse_dir(block, 500);
+ /* With the fix this returns NULL at TB_PROPERTY_MAX_DEPTH (8).
+ * Without it, the kernel stack-guard fires ~50-80 frames in
+ * and the kunit thread oopses. */
+ KUNIT_EXPECT_NULL(test, dir);
+ tb_property_free_dir(dir);
+}
+
+static void tb_test_property_parse_dir_len_underflow(struct kunit *test)
+{
+ u32 *block = kunit_kzalloc(test, 500 * sizeof(u32), GFP_KERNEL);
+ struct tb_property_dir *dir;
+ struct entry {
+ u32 key_hi, key_lo;
+ u16 length;
+ u8 reserved;
+ u8 type;
+ u32 value;
+ } *e;
+
+ block[0] = 0x55584401;
+ block[1] = 4;
+
+ /* DIRECTORY entry with length=3. When parsed as non-root,
+ * content_len = dir_len - 4 underflows size_t to ~SIZE_MAX,
+ * nentries = SIZE_MAX/4. The for-loop walks entries past the
+ * block, reading OOB on each iteration.
+ */
+ e = (void *)&block[2];
+ e->key_hi = 0x61616161;
+ e->key_lo = 0x61616161;
+ e->length = 3;
+ e->type = 0x44;
+ e->value = 6;
+
+ dir = tb_property_parse_dir(block, 500);
+ /* With the fix: NULL. Without: KASAN splat on
+ * block[content_offset + i*4] for i > 124 (past the 500-dword
+ * block). */
+ 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