[PATCH 1/6] thunderbolt: reject zero-length property entries in validator

[Michael Bommarito <michael.bommarito@gmail.com>]

tb_property_entry_valid() accepts entries with length == 0 for
DIRECTORY, DATA, and TEXT types.  A zero-length TEXT entry passes
validation but causes an underflow in the null-termination logic:

  property->value.text[property->length * 4 - 1] = '\0';

When property->length is 0 this writes to offset -1 relative to
the allocation.

Reject zero-length entries early in the validator since they have no
valid representation in the XDomain property protocol.

Fixes: cdae7c07e3e3 ("thunderbolt: Add support for XDomain properties")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
 drivers/thunderbolt/property.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/thunderbolt/property.c b/drivers/thunderbolt/property.c
index da2c59a17db5c..5cbc1c4f159c2 100644
--- a/drivers/thunderbolt/property.c
+++ b/drivers/thunderbolt/property.c
@@ -60,6 +60,8 @@ static bool tb_property_entry_valid(const struct tb_property_entry *entry,
 	case TB_PROPERTY_TYPE_DIRECTORY:
 	case TB_PROPERTY_TYPE_DATA:
 	case TB_PROPERTY_TYPE_TEXT:
+		if (!entry->length)
+			return false;
 		if (entry->length > block_len)
 			return false;
 		if (check_add_overflow(entry->value, entry->length, &end) ||

base-commit: 928abe19fbf0127003abcb1ea69cabc1c897d0ab
-- 
2.53.0