From b09a1d237f1a881c82c4cd9381a9fc3d56cb22e2 Mon Sep 17 00:00:00 2001
From: Steven Moreland <smoreland@google.com>
Date: Sat, 7 Dec 2024 03:23:57 +0000
Subject: binder_parcel_fuzzer: support owned Parcels

Some codepaths in Parcel are different when the Parcel
is owned. This allows fillRandomParcel to also sometimes
cause the returned Parcel be a view of a filled out
Parcel. This increases the possible impact and bug
finding abilities of all of our AIDL fuzzers as well.

Ignore-AOSP-First: fuzzing
Bug: 369404061
Test: binder_parcel_fuzzer
Change-Id: Ib19a0cbd74d48e18ba36cff56202541105ef9163
---
 libs/binder/Parcel.cpp | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

(limited to 'libs/binder/Parcel.cpp')

diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index e2eea6c458..0b7cd8154d 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -2728,6 +2728,65 @@ size_t Parcel::ipcObjectsCount() const
     return 0;
 }
 
+static void do_nothing_release_func(const uint8_t* data, size_t dataSize,
+                                    const binder_size_t* objects, size_t objectsCount) {
+    (void)data;
+    (void)dataSize;
+    (void)objects;
+    (void)objectsCount;
+}
+static void delete_data_release_func(const uint8_t* data, size_t dataSize,
+                                     const binder_size_t* objects, size_t objectsCount) {
+    delete[] data;
+    (void)dataSize;
+    (void)objects;
+    (void)objectsCount;
+}
+
+void Parcel::makeDangerousViewOf(Parcel* p) {
+    if (p->isForRpc()) {
+        // warning: this must match the logic in rpcSetDataReference
+        auto* rf = p->maybeRpcFields();
+        LOG_ALWAYS_FATAL_IF(rf == nullptr);
+        std::vector<std::variant<binder::unique_fd, binder::borrowed_fd>> fds;
+        if (rf->mFds) {
+            fds.reserve(rf->mFds->size());
+            for (const auto& fd : *rf->mFds) {
+                fds.push_back(binder::borrowed_fd(toRawFd(fd)));
+            }
+        }
+        status_t result =
+                rpcSetDataReference(rf->mSession, p->mData, p->mDataSize,
+                                    rf->mObjectPositions.data(), rf->mObjectPositions.size(),
+                                    std::move(fds), do_nothing_release_func);
+        LOG_ALWAYS_FATAL_IF(result != OK, "Failed: %s", statusToString(result).c_str());
+    } else {
+#ifdef BINDER_WITH_KERNEL_IPC
+        // warning: this must match the logic in ipcSetDataReference
+        auto* kf = p->maybeKernelFields();
+        LOG_ALWAYS_FATAL_IF(kf == nullptr);
+
+        // Ownership of FDs is passed to the Parcel from kernel binder. This should be refactored
+        // to move this ownership out of Parcel and into release_func. However, today, Parcel
+        // always assums it can own and close FDs today. So, for purposes of testing consistency,
+        // , create new FDs it can own.
+
+        uint8_t* newData = new uint8_t[p->mDataSize]; // deleted by delete_data_release_func
+        memcpy(newData, p->mData, p->mDataSize);
+        for (size_t i = 0; i < kf->mObjectsSize; i++) {
+            flat_binder_object* flat =
+                    reinterpret_cast<flat_binder_object*>(newData + kf->mObjects[i]);
+            if (flat->hdr.type == BINDER_TYPE_FD) {
+                flat->handle = fcntl(flat->handle, F_DUPFD_CLOEXEC, 0);
+            }
+        }
+
+        ipcSetDataReference(newData, p->mDataSize, kf->mObjects, kf->mObjectsSize,
+                            delete_data_release_func);
+#endif // BINDER_WITH_KERNEL_IPC
+    }
+}
+
 void Parcel::ipcSetDataReference(const uint8_t* data, size_t dataSize, const binder_size_t* objects,
                                  size_t objectsCount, release_func relFunc) {
     // this code uses 'mOwner == nullptr' to understand whether it owns memory
@@ -2738,6 +2797,7 @@ void Parcel::ipcSetDataReference(const uint8_t* data, size_t dataSize, const bin
     auto* kernelFields = maybeKernelFields();
     LOG_ALWAYS_FATAL_IF(kernelFields == nullptr); // guaranteed by freeData.
 
+    // must match makeDangerousViewOf
     mData = const_cast<uint8_t*>(data);
     mDataSize = mDataCapacity = dataSize;
     kernelFields->mObjects = const_cast<binder_size_t*>(objects);
@@ -2816,6 +2876,7 @@ status_t Parcel::rpcSetDataReference(
     auto* rpcFields = maybeRpcFields();
     LOG_ALWAYS_FATAL_IF(rpcFields == nullptr); // guaranteed by markForRpc.
 
+    // must match makeDangerousViewOf
     mData = const_cast<uint8_t*>(data);
     mDataSize = mDataCapacity = dataSize;
     mOwner = relFunc;
-- 
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