[lldb] Ensure FILE* access mode is correctly specified when creating a NativeFile. (#167764)

ashgti · web-flow · commit bb9df2e3bd7e · 2025-11-17T10:51:13.000-08:00
If we open a `NativeFile` with a `FILE*`, the OpenOptions default to `eOpenOptionReadOnly`. This is an issue in python scripts if you try to write to one of the files like `print("Hi", file=lldb.debugger.GetOutputFileHandle())`. To address this, we need to specify the access mode whenever we create a `NativeFile` from a `FILE*`. I also added an assert on the `NativeFile` that validates the file is opened with the correct access mode and updated `NativeFile::Read` and `NativeFile::Write` to check the access mode. Before these changes: ``` $ lldb -b -O 'script lldb.debugger.GetOutputFileHandle().write("abc")' (lldb) script lldb.debugger.GetOutputFileHandle().write("abc") Traceback (most recent call last): File "<input>", line 1, in <module> io.UnsupportedOperation: not writable ``` After: ``` $ lldb -b -O 'script lldb.debugger.GetOutputFileHandle().write("abc")' (lldb) script lldb.debugger.GetOutputFileHandle().write("abc") abc3 ``` Fixes #122387
diff --git a/lldb/include/lldb/API/SBFile.h b/lldb/include/lldb/API/SBFile.h
@@ -27,7 +27,10 @@ class LLDB_API SBFile {
   SBFile(FileSP file_sp);
 #ifndef SWIG
   SBFile(const SBFile &rhs);
+  LLDB_DEPRECATED_FIXME("Use the constructor that specifies mode instead",
+                        "SBFile(FILE*, const char*, bool)")
   SBFile(FILE *file, bool transfer_ownership);
+  SBFile(FILE *file, const char *mode, bool transfer_ownership);
 #endif
   SBFile(int fd, const char *mode, bool transfer_ownership);
   ~SBFile();
diff --git a/lldb/include/lldb/Host/File.h b/lldb/include/lldb/Host/File.h
@@ -66,6 +66,9 @@ class File : public IOObject {
     LLVM_MARK_AS_BITMASK_ENUM(/* largest_value= */ eOpenOptionInvalid)
   };
 
+  static constexpr OpenOptions OpenOptionsModeMask =
+      eOpenOptionReadOnly | eOpenOptionWriteOnly | eOpenOptionReadWrite;
+
   static mode_t ConvertOpenOptionsForPOSIXOpen(OpenOptions open_options);
   static llvm::Expected<OpenOptions> GetOptionsFromMode(llvm::StringRef mode);
   static bool DescriptorIsValid(int descriptor) { return descriptor >= 0; };
@@ -384,7 +387,7 @@ class NativeFile : public File {
 
   NativeFile();
 
-  NativeFile(FILE *fh, bool transfer_ownership);
+  NativeFile(FILE *fh, OpenOptions options, bool transfer_ownership);
 
   NativeFile(int fd, OpenOptions options, bool transfer_ownership);
 
diff --git a/lldb/include/lldb/Host/StreamFile.h b/lldb/include/lldb/Host/StreamFile.h
@@ -81,7 +81,8 @@ class LockableStreamFile {
   LockableStreamFile(StreamFile &stream_file, Mutex &mutex)
       : m_file_sp(stream_file.GetFileSP()), m_mutex(mutex) {}
   LockableStreamFile(FILE *fh, bool transfer_ownership, Mutex &mutex)
-      : m_file_sp(std::make_shared<NativeFile>(fh, transfer_ownership)),
+      : m_file_sp(std::make_shared<NativeFile>(fh, File::eOpenOptionWriteOnly,
+                                               transfer_ownership)),
         m_mutex(mutex) {}
   LockableStreamFile(std::shared_ptr<File> file_sp, Mutex &mutex)
       : m_file_sp(file_sp), m_mutex(mutex) {}
diff --git a/lldb/source/API/SBCommandReturnObject.cpp b/lldb/source/API/SBCommandReturnObject.cpp
@@ -15,6 +15,7 @@
 #include "lldb/API/SBValue.h"
 #include "lldb/API/SBValueList.h"
 #include "lldb/Core/StructuredDataImpl.h"
+#include "lldb/Host/File.h"
 #include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/Instrumentation.h"
@@ -275,14 +276,16 @@ void SBCommandReturnObject::SetImmediateErrorFile(FILE *fh) {
 void SBCommandReturnObject::SetImmediateOutputFile(FILE *fh,
                                                    bool transfer_ownership) {
   LLDB_INSTRUMENT_VA(this, fh, transfer_ownership);
-  FileSP file = std::make_shared<NativeFile>(fh, transfer_ownership);
+  FileSP file = std::make_shared<NativeFile>(fh, File::eOpenOptionWriteOnly,
+                                             transfer_ownership);
   ref().SetImmediateOutputFile(file);
 }
 
 void SBCommandReturnObject::SetImmediateErrorFile(FILE *fh,
                                                   bool transfer_ownership) {
   LLDB_INSTRUMENT_VA(this, fh, transfer_ownership);
-  FileSP file = std::make_shared<NativeFile>(fh, transfer_ownership);
+  FileSP file = std::make_shared<NativeFile>(fh, File::eOpenOptionWriteOnly,
+                                             transfer_ownership);
   ref().SetImmediateErrorFile(file);
 }
 
diff --git a/lldb/source/API/SBDebugger.cpp b/lldb/source/API/SBDebugger.cpp
@@ -327,8 +327,8 @@ void SBDebugger::SkipAppInitFiles(bool b) {
 void SBDebugger::SetInputFileHandle(FILE *fh, bool transfer_ownership) {
   LLDB_INSTRUMENT_VA(this, fh, transfer_ownership);
   if (m_opaque_sp)
-    m_opaque_sp->SetInputFile(
-        (FileSP)std::make_shared<NativeFile>(fh, transfer_ownership));
+    m_opaque_sp->SetInputFile((FileSP)std::make_shared<NativeFile>(
+        fh, File::eOpenOptionReadOnly, transfer_ownership));
 }
 
 SBError SBDebugger::SetInputString(const char *data) {
@@ -385,7 +385,8 @@ SBError SBDebugger::SetOutputFile(FileSP file_sp) {
 
 void SBDebugger::SetOutputFileHandle(FILE *fh, bool transfer_ownership) {
   LLDB_INSTRUMENT_VA(this, fh, transfer_ownership);
-  SetOutputFile((FileSP)std::make_shared<NativeFile>(fh, transfer_ownership));
+  SetOutputFile((FileSP)std::make_shared<NativeFile>(
+      fh, File::eOpenOptionWriteOnly, transfer_ownership));
 }
 
 SBError SBDebugger::SetOutputFile(SBFile file) {
@@ -405,7 +406,8 @@ SBError SBDebugger::SetOutputFile(SBFile file) {
 
 void SBDebugger::SetErrorFileHandle(FILE *fh, bool transfer_ownership) {
   LLDB_INSTRUMENT_VA(this, fh, transfer_ownership);
-  SetErrorFile((FileSP)std::make_shared<NativeFile>(fh, transfer_ownership));
+  SetErrorFile((FileSP)std::make_shared<NativeFile>(
+      fh, File::eOpenOptionWriteOnly, transfer_ownership));
 }
 
 SBError SBDebugger::SetErrorFile(FileSP file_sp) {
@@ -576,8 +578,10 @@ void SBDebugger::HandleProcessEvent(const SBProcess &process,
                                     FILE *err) {
   LLDB_INSTRUMENT_VA(this, process, event, out, err);
 
-  FileSP outfile = std::make_shared<NativeFile>(out, false);
-  FileSP errfile = std::make_shared<NativeFile>(err, false);
+  FileSP outfile =
+      std::make_shared<NativeFile>(out, File::eOpenOptionWriteOnly, false);
+  FileSP errfile =
+      std::make_shared<NativeFile>(err, File::eOpenOptionWriteOnly, false);
   return HandleProcessEvent(process, event, outfile, errfile);
 }
 
diff --git a/lldb/source/API/SBFile.cpp b/lldb/source/API/SBFile.cpp
@@ -39,7 +39,22 @@ SBFile::SBFile() { LLDB_INSTRUMENT_VA(this); }
 SBFile::SBFile(FILE *file, bool transfer_ownership) {
   LLDB_INSTRUMENT_VA(this, file, transfer_ownership);
 
-  m_opaque_sp = std::make_shared<NativeFile>(file, transfer_ownership);
+  // For backwards comptability, this defaulted to ReadOnly previously.
+  m_opaque_sp = std::make_shared<NativeFile>(file, File::eOpenOptionReadOnly,
+                                             transfer_ownership);
+}
+
+SBFile::SBFile(FILE *file, const char *mode, bool transfer_ownership) {
+  LLDB_INSTRUMENT_VA(this, file, transfer_ownership);
+
+  auto options = File::GetOptionsFromMode(mode);
+  if (!options) {
+    llvm::consumeError(options.takeError());
+    return;
+  }
+
+  m_opaque_sp =
+      std::make_shared<NativeFile>(file, options.get(), transfer_ownership);
 }
 
 SBFile::SBFile(int fd, const char *mode, bool transfer_owndership) {
diff --git a/lldb/source/API/SBInstruction.cpp b/lldb/source/API/SBInstruction.cpp
@@ -10,8 +10,8 @@
 #include "lldb/Utility/Instrumentation.h"
 
 #include "lldb/API/SBAddress.h"
-#include "lldb/API/SBFrame.h"
 #include "lldb/API/SBFile.h"
+#include "lldb/API/SBFrame.h"
 
 #include "lldb/API/SBStream.h"
 #include "lldb/API/SBTarget.h"
@@ -268,7 +268,8 @@ bool SBInstruction::GetDescription(lldb::SBStream &s) {
 
 void SBInstruction::Print(FILE *outp) {
   LLDB_INSTRUMENT_VA(this, outp);
-  FileSP out = std::make_shared<NativeFile>(outp, /*take_ownership=*/false);
+  FileSP out = std::make_shared<NativeFile>(outp, File::eOpenOptionWriteOnly,
+                                            /*take_ownership=*/false);
   Print(out);
 }
 
diff --git a/lldb/source/API/SBProcess.cpp b/lldb/source/API/SBProcess.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "lldb/API/SBProcess.h"
+#include "lldb/Host/File.h"
 #include "lldb/Utility/Instrumentation.h"
 
 #include <cinttypes>
@@ -310,7 +311,8 @@ void SBProcess::ReportEventState(const SBEvent &event, SBFile out) const {
 
 void SBProcess::ReportEventState(const SBEvent &event, FILE *out) const {
   LLDB_INSTRUMENT_VA(this, event, out);
-  FileSP outfile = std::make_shared<NativeFile>(out, false);
+  FileSP outfile =
+      std::make_shared<NativeFile>(out, File::eOpenOptionWriteOnly, false);
   return ReportEventState(event, outfile);
 }
 
diff --git a/lldb/source/API/SBStream.cpp b/lldb/source/API/SBStream.cpp
@@ -116,7 +116,8 @@ void SBStream::RedirectToFile(const char *path, bool append) {
 
 void SBStream::RedirectToFileHandle(FILE *fh, bool transfer_fh_ownership) {
   LLDB_INSTRUMENT_VA(this, fh, transfer_fh_ownership);
-  FileSP file = std::make_unique<NativeFile>(fh, transfer_fh_ownership);
+  FileSP file = std::make_unique<NativeFile>(fh, File::eOpenOptionReadWrite,
+                                             transfer_fh_ownership);
   return RedirectToFile(file);
 }
 
diff --git a/lldb/source/Core/Debugger.cpp b/lldb/source/Core/Debugger.cpp
@@ -965,7 +965,8 @@ llvm::StringRef Debugger::GetStaticBroadcasterClass() {
 Debugger::Debugger(lldb::LogOutputCallback log_callback, void *baton)
     : UserID(g_unique_id++),
       Properties(std::make_shared<OptionValueProperties>()),
-      m_input_file_sp(std::make_shared<NativeFile>(stdin, NativeFile::Unowned)),
+      m_input_file_sp(std::make_shared<NativeFile>(
+          stdin, File::eOpenOptionReadOnly, NativeFile::Unowned)),
       m_output_stream_sp(std::make_shared<LockableStreamFile>(
           stdout, NativeFile::Unowned, m_output_mutex)),
       m_error_stream_sp(std::make_shared<LockableStreamFile>(
@@ -1172,7 +1173,8 @@ Status Debugger::SetInputString(const char *data) {
     return result;
   }
 
-  SetInputFile((FileSP)std::make_shared<NativeFile>(commands_file, true));
+  SetInputFile((FileSP)std::make_shared<NativeFile>(
+      commands_file, File::eOpenOptionReadOnly, true));
   return result;
 }
 
@@ -1378,7 +1380,8 @@ void Debugger::AdoptTopIOHandlerFilesIfInvalid(FileSP &in,
       in = GetInputFileSP();
     // If there is nothing, use stdin
     if (!in)
-      in = std::make_shared<NativeFile>(stdin, NativeFile::Unowned);
+      in = std::make_shared<NativeFile>(stdin, File::eOpenOptionReadOnly,
+                                        NativeFile::Unowned);
   }
   // If no STDOUT has been set, then set it appropriately
   if (!out || !out->GetUnlockedFile().IsValid()) {
diff --git a/lldb/source/Host/common/File.cpp b/lldb/source/Host/common/File.cpp
@@ -249,15 +249,35 @@ uint32_t File::GetPermissions(Status &error) const {
 
 NativeFile::NativeFile() = default;
 
-NativeFile::NativeFile(FILE *fh, bool transfer_ownership)
-    : m_stream(fh), m_own_stream(transfer_ownership) {
+NativeFile::NativeFile(FILE *fh, OpenOptions options, bool transfer_ownership)
+    : m_stream(fh), m_options(options), m_own_stream(transfer_ownership) {
 #ifdef _WIN32
   // In order to properly display non ASCII characters in Windows, we need to
   // use Windows APIs to print to the console. This is only required if the
   // stream outputs to a console.
   int fd = _fileno(fh);
   is_windows_console =
       ::GetFileType((HANDLE)::_get_osfhandle(fd)) == FILE_TYPE_CHAR;
+#else
+#ifndef NDEBUG
+  int fd = fileno(fh);
+  if (fd != -1) {
+    int required_mode = ConvertOpenOptionsForPOSIXOpen(options) & O_ACCMODE;
+    int mode = fcntl(fd, F_GETFL);
+    if (mode != -1) {
+      mode &= O_ACCMODE;
+      // Check that the file is open with a valid subset of the requested file
+      // access mode, e.g. if we expected the file to be writable then ensure it
+      // was opened with O_WRONLY or O_RDWR.
+      assert(
+          (required_mode == O_RDWR && mode == O_RDWR) ||
+          (required_mode == O_RDONLY && (mode == O_RDWR || mode == O_RDONLY) ||
+           (required_mode == O_WRONLY &&
+            (mode == O_RDWR || mode == O_WRONLY))) &&
+              "invalid file access mode");
+    }
+  }
+#endif
 #endif
 }
 
@@ -274,7 +294,8 @@ NativeFile::NativeFile(int fd, OpenOptions options, bool transfer_ownership)
 }
 
 bool NativeFile::IsValid() const {
-  std::scoped_lock<std::mutex, std::mutex> lock(m_descriptor_mutex, m_stream_mutex);
+  std::scoped_lock<std::mutex, std::mutex> lock(m_descriptor_mutex,
+                                                m_stream_mutex);
   return DescriptorIsValidUnlocked() || StreamIsValidUnlocked();
 }
 
@@ -343,7 +364,8 @@ FILE *NativeFile::GetStream() {
 }
 
 Status NativeFile::Close() {
-  std::scoped_lock<std::mutex, std::mutex> lock(m_descriptor_mutex, m_stream_mutex);
+  std::scoped_lock<std::mutex, std::mutex> lock(m_descriptor_mutex,
+                                                m_stream_mutex);
 
   Status error;
 
@@ -548,6 +570,10 @@ Status NativeFile::Sync() {
 Status NativeFile::Read(void *buf, size_t &num_bytes) {
   Status error;
 
+  // Ensure the file is open for reading.
+  if ((m_options & File::OpenOptionsModeMask) == eOpenOptionWriteOnly)
+    return Status(std::make_error_code(std::errc::bad_file_descriptor));
+
 #if defined(MAX_READ_SIZE)
   if (num_bytes > MAX_READ_SIZE) {
     uint8_t *p = (uint8_t *)buf;
@@ -612,6 +638,10 @@ Status NativeFile::Read(void *buf, size_t &num_bytes) {
 Status NativeFile::Write(const void *buf, size_t &num_bytes) {
   Status error;
 
+  // Ensure the file is open for writing.
+  if ((m_options & File::OpenOptionsModeMask) == File::eOpenOptionReadOnly)
+    return Status(std::make_error_code(std::errc::bad_file_descriptor));
+
 #if defined(MAX_WRITE_SIZE)
   if (num_bytes > MAX_WRITE_SIZE) {
     const uint8_t *p = (const uint8_t *)buf;
@@ -776,8 +806,8 @@ Status NativeFile::Write(const void *buf, size_t &num_bytes, off_t &offset) {
   int fd = GetDescriptor();
   if (fd != kInvalidDescriptor) {
 #ifndef _WIN32
-    ssize_t bytes_written =
-        llvm::sys::RetryAfterSignal(-1, ::pwrite, m_descriptor, buf, num_bytes, offset);
+    ssize_t bytes_written = llvm::sys::RetryAfterSignal(
+        -1, ::pwrite, m_descriptor, buf, num_bytes, offset);
     if (bytes_written < 0) {
       num_bytes = 0;
       error = Status::FromErrno();
diff --git a/lldb/source/Host/common/StreamFile.cpp b/lldb/source/Host/common/StreamFile.cpp
@@ -27,7 +27,8 @@ StreamFile::StreamFile(int fd, bool transfer_ownership) : Stream() {
 }
 
 StreamFile::StreamFile(FILE *fh, bool transfer_ownership) : Stream() {
-  m_file_sp = std::make_shared<NativeFile>(fh, transfer_ownership);
+  m_file_sp = std::make_shared<NativeFile>(fh, File::eOpenOptionWriteOnly,
+                                           transfer_ownership);
 }
 
 StreamFile::StreamFile(const char *path, File::OpenOptions options,
diff --git a/lldb/unittests/Host/FileTest.cpp b/lldb/unittests/Host/FileTest.cpp
@@ -8,6 +8,7 @@
 
 #include "lldb/Host/File.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/Path.h"
@@ -35,7 +36,7 @@ TEST(File, GetWaitableHandleFileno) {
   FILE *stream = fdopen(fd, "r");
   ASSERT_TRUE(stream);
 
-  NativeFile file(stream, true);
+  NativeFile file(stream, File::eOpenOptionReadWrite, true);
 #ifdef _WIN32
   EXPECT_EQ(file.GetWaitableHandle(), (HANDLE)_get_osfhandle(fd));
 #else
@@ -67,3 +68,22 @@ TEST(File, GetStreamFromDescriptor) {
   EXPECT_EQ(file.GetWaitableHandle(), (file_t)fd);
 #endif
 }
+
+TEST(File, ReadOnlyModeNotWritable) {
+  const auto *Info = testing::UnitTest::GetInstance()->current_test_info();
+  llvm::SmallString<128> name;
+  int fd;
+  llvm::sys::fs::createTemporaryFile(llvm::Twine(Info->test_case_name()) + "-" +
+                                         Info->name(),
+                                     "test", fd, name);
+
+  llvm::FileRemover remover(name);
+  ASSERT_GE(fd, 0);
+
+  NativeFile file(fd, File::eOpenOptionReadOnly, true);
+  ASSERT_TRUE(file.IsValid());
+  llvm::StringLiteral buf = "Hello World";
+  size_t bytes_written = buf.size();
+  Status error = file.Write(buf.data(), bytes_written);
+  EXPECT_EQ(error.Fail(), true);
+}

Original file line number	Diff line number	Diff line change
`@@ -116,7 +116,8 @@ void SBStream::RedirectToFile(const char *path, bool append) {`
`116`	`116`
`117`	`117`	`void SBStream::RedirectToFileHandle(FILE *fh, bool transfer_fh_ownership) {`
`118`	`118`	`LLDB_INSTRUMENT_VA(this, fh, transfer_fh_ownership);`
`119`		`- FileSP file = std::make_unique<NativeFile>(fh, transfer_fh_ownership);`
	`119`	`+ FileSP file = std::make_unique<NativeFile>(fh, File::eOpenOptionReadWrite,`
	`120`	`+ transfer_fh_ownership);`
`120`	`121`	`return RedirectToFile(file);`
`121`	`122`	`}`
`122`	`123`