From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Brian Delwiche <delwiche@google.com>
Date: Fri, 19 May 2023 19:17:16 +0000
Subject: [PATCH] Fix integer overflow in build_read_multi_rsp

Local variables tracking structure size in build_read_multi_rsp are of
uint16 type but accept a full uint16 range from function arguments while
appending a fixed-length offset.  This can lead to an integer overflow
and unexpected behavior.

Change the locals to size_t, and add a check during reasssignment.

Bug: 273966636
Test: atest bluetooth_test_gd_unit, net_test_stack_btm
Tag: #security
Ignore-AOSP-First: Security
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:53f64274cbf2268ad6db5af9c61ceead9ef64fb0)
Merged-In: Iff252f0dd06aac9776e8548631e0b700b3ed85b9
Change-Id: Iff252f0dd06aac9776e8548631e0b700b3ed85b9
---
 stack/gatt/gatt_sr.cc | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/stack/gatt/gatt_sr.cc b/stack/gatt/gatt_sr.cc
index 0f32cde37..ee5059b92 100644
--- a/stack/gatt/gatt_sr.cc
+++ b/stack/gatt/gatt_sr.cc
@@ -114,7 +114,8 @@ void gatt_dequeue_sr_cmd(tGATT_TCB& tcb) {
  ******************************************************************************/
 static bool process_read_multi_rsp(tGATT_SR_CMD* p_cmd, tGATT_STATUS status,
                                    tGATTS_RSP* p_msg, uint16_t mtu) {
-  uint16_t ii, total_len, len;
+  uint16_t ii;
+  size_t total_len, len;
   uint8_t* p;
   bool is_overflow = false;
 
@@ -169,16 +170,22 @@ static bool process_read_multi_rsp(tGATT_SR_CMD* p_cmd, tGATT_STATUS status,
             len = p_rsp->attr_value.len - (total_len - mtu);
             is_overflow = true;
             VLOG(1) << StringPrintf(
-                "multi read overflow available len=%d val_len=%d", len,
+                "multi read overflow available len=%zu val_len=%d", len,
                 p_rsp->attr_value.len);
           } else {
             len = p_rsp->attr_value.len;
           }
 
           if (p_rsp->attr_value.handle == p_cmd->multi_req.handles[ii]) {
-            memcpy(p, p_rsp->attr_value.value, len);
-            if (!is_overflow) p += len;
-            p_buf->len += len;
+            // check for possible integer overflow
+            if (p_buf->len + len <= UINT16_MAX) {
+              memcpy(p, p_rsp->attr_value.value, len);
+              if (!is_overflow) p += len;
+              p_buf->len += len;
+            } else {
+              p_cmd->status = GATT_NOT_FOUND;
+              break;
+            }
           } else {
             p_cmd->status = GATT_NOT_FOUND;
             break;
