[PATCH BlueZ v2 7/8] shared/gatt-client: Check value lengths before reading them

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Check the iterator result when reading the Database Hash and avoid
reading the Extended Properties value when the response is empty.

Fixes: 0f67d5e2f19f ("shared/gatt-client: Read database hash if available")
Fixes: 6b3f0f3ab935 ("gatt-client: Read extended props on service discovery")
Assisted-by: OpenCode:claude-opus-5.5
---
 src/shared/gatt-client.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/shared/gatt-client.c b/src/shared/gatt-client.c
index 4a8bdfc441d4..a923699b74bb 100644
--- a/src/shared/gatt-client.c
+++ b/src/shared/gatt-client.c
@@ -887,7 +887,8 @@ static void ext_prop_read_cb(bool success, uint8_t att_ecode,
 	if (!success)
 		goto done;
 
-	DBG(client, "Ext. prop value: 0x%04x", (uint16_t)value[0]);
+	DBG(client, "Ext. prop value: 0x%04x",
+				length ? (uint16_t)value[0] : 0);
 
 	desc_attr = queue_pop_head(op->ext_prop_desc);
 	if (!desc_attr)
@@ -1475,8 +1476,10 @@ static void db_hash_read_cb(bool success, uint8_t att_ecode,
 	if (!success)
 		goto discover;
 
-	bt_gatt_iter_init(&iter, result);
-	bt_gatt_iter_next_read_by_type(&iter, &handle, &len, &value);
+	if (!bt_gatt_iter_init(&iter, result) ||
+			!bt_gatt_iter_next_read_by_type(&iter, &handle,
+							&len, &value))
+		goto discover;
 
 	DBG(client, "DB Hash found: handle 0x%04x length 0x%04x",
 							handle, len);
-- 
2.56.0