From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: tyiu <tyiu@google.com>
Date: Tue, 28 Mar 2023 18:40:51 +0000
Subject: [PATCH] Fix gatt_end_operation buffer overflow

Added boundary check for gatt_end_operation to prevent writing out of
boundary.

Since response of the GATT server is handled in
gatt_client_handle_server_rsp() and gatt_process_read_rsp(), the maximum
lenth that can be passed into the handlers is bounded by
GATT_MAX_MTU_SIZE, which is set to 517, which is greater than
GATT_MAX_ATTR_LEN which is set to 512. The fact that there is no spec
that gaurentees MTU response to be less than or equal to 512 bytes can
cause a buffer overflow when performing memcpy without length check.

Bug: 261068592
Test: No test since not affecting behavior
Tag: #security
Ignore-AOSP-First: security
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:dd7298e982e4bbf0138a490562679c9a4a755200)
Merged-In: I49e2797cd9300ee4cd69f2c7fa5f0073db78b873
Change-Id: I49e2797cd9300ee4cd69f2c7fa5f0073db78b873
---
 stack/gatt/gatt_utils.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/stack/gatt/gatt_utils.cc b/stack/gatt/gatt_utils.cc
index 291cd1062..eb2a12dbc 100644
--- a/stack/gatt/gatt_utils.cc
+++ b/stack/gatt/gatt_utils.cc
@@ -1198,6 +1198,13 @@ void gatt_end_operation(tGATT_CLCB* p_clcb, tGATT_STATUS status, void* p_data) {
       cb_data.att_value.handle = p_clcb->s_handle;
       cb_data.att_value.len = p_clcb->counter;
 
+      if (cb_data.att_value.len > GATT_MAX_ATTR_LEN) {
+        LOG(WARNING) << __func__
+                     << StringPrintf(" Large cb_data.att_value, size=%d",
+                                     cb_data.att_value.len);
+        cb_data.att_value.len = GATT_MAX_ATTR_LEN;
+      }
+
       if (p_data && p_clcb->counter)
         memcpy(cb_data.att_value.value, p_data, cb_data.att_value.len);
     }
