Reland: Fix an OOB write bug in attp_build_value_cmd
Bug: 295887535
Bug: 315127634
Test: m com.android.btservices
Test: atest net_test_stack_gatt
Ignore-AOSP-First: security
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:4ae5e736813bf2928bfc8c71e3dacf3b78394046)
Merged-In: I291fd665a68d90813b8c21c80d23cc438f84f285
Change-Id: I291fd665a68d90813b8c21c80d23cc438f84f285
diff --git a/system/stack/gatt/att_protocol.cc b/system/stack/gatt/att_protocol.cc
index 29ceec2..c8c6f24 100644
--- a/system/stack/gatt/att_protocol.cc
+++ b/system/stack/gatt/att_protocol.cc
@@ -286,46 +286,80 @@
static BT_HDR* attp_build_value_cmd(uint16_t payload_size, uint8_t op_code,
uint16_t handle, uint16_t offset,
uint16_t len, uint8_t* p_data) {
- uint8_t *p, *pp, pair_len, *p_pair_len;
+ uint8_t *p, *pp, *p_pair_len;
+ size_t pair_len;
+ size_t size_now = 1;
+
+#define CHECK_SIZE() \
+ do { \
+ if (size_now > payload_size) { \
+ LOG_ERROR("payload size too small"); \
+ osi_free(p_buf); \
+ return nullptr; \
+ } \
+ } while (false)
+
BT_HDR* p_buf =
(BT_HDR*)osi_malloc(sizeof(BT_HDR) + payload_size + L2CAP_MIN_OFFSET);
p = pp = (uint8_t*)(p_buf + 1) + L2CAP_MIN_OFFSET;
+
+ CHECK_SIZE();
UINT8_TO_STREAM(p, op_code);
p_buf->offset = L2CAP_MIN_OFFSET;
- p_buf->len = 1;
if (op_code == GATT_RSP_READ_BY_TYPE) {
- p_pair_len = p;
+ p_pair_len = p++;
pair_len = len + 2;
- UINT8_TO_STREAM(p, pair_len);
- p_buf->len += 1;
+ size_now += 1;
+ CHECK_SIZE();
+ // this field will be backfilled in the end of this function
}
+
if (op_code != GATT_RSP_READ_BLOB && op_code != GATT_RSP_READ) {
+ size_now += 2;
+ CHECK_SIZE();
UINT16_TO_STREAM(p, handle);
- p_buf->len += 2;
}
if (op_code == GATT_REQ_PREPARE_WRITE || op_code == GATT_RSP_PREPARE_WRITE) {
+ size_now += 2;
+ CHECK_SIZE();
UINT16_TO_STREAM(p, offset);
- p_buf->len += 2;
}
if (len > 0 && p_data != NULL) {
/* ensure data not exceed MTU size */
- if (payload_size - p_buf->len < len) {
- len = payload_size - p_buf->len;
+ if (payload_size - size_now < len) {
+ len = payload_size - size_now;
/* update handle value pair length */
- if (op_code == GATT_RSP_READ_BY_TYPE) *p_pair_len = (len + 2);
+ if (op_code == GATT_RSP_READ_BY_TYPE) {
+ pair_len = (len + 2);
+ }
LOG(WARNING) << StringPrintf(
"attribute value too long, to be truncated to %d", len);
}
+ size_now += len;
+ CHECK_SIZE();
ARRAY_TO_STREAM(p, p_data, len);
- p_buf->len += len;
}
+ // backfill pair len field
+ if (op_code == GATT_RSP_READ_BY_TYPE) {
+ if (pair_len > UINT8_MAX) {
+ LOG_ERROR("pair_len greater than %d", UINT8_MAX);
+ osi_free(p_buf);
+ return nullptr;
+ }
+
+ *p_pair_len = (uint8_t)pair_len;
+ }
+
+#undef CHECK_SIZE
+
+ p_buf->len = (uint16_t)size_now;
return p_buf;
}