[Lldb-commits] [lldb] d9c5613 - Update logic to close inherited file descriptors.

[Rumeet Dhindsa via lldb-commits]

Author: Rumeet Dhindsa
Date: 2021-08-19T14:40:43-07:00
New Revision: d9c5613e856cf2addfbf892fc4c1ce9ef9feceaa

URL: https://github.com/llvm/llvm-project/commit/d9c5613e856cf2addfbf892fc4c1ce9ef9feceaa
DIFF: https://github.com/llvm/llvm-project/commit/d9c5613e856cf2addfbf892fc4c1ce9ef9feceaa.diff

LOG: Update logic to close inherited file descriptors.

This patch adds the support to close all inherited fds into the child
process by iterating over /proc/self/fd entries.

Differential Revision: https://reviews.llvm.org/D105732

Added: 
    

Modified: 
    lldb/source/Host/posix/ProcessLauncherPosixFork.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/source/Host/posix/ProcessLauncherPosixFork.cpp b/lldb/source/Host/posix/ProcessLauncherPosixFork.cpp
index b49b541927afe..63178e6c8a7a7 100644
--- a/lldb/source/Host/posix/ProcessLauncherPosixFork.cpp
+++ b/lldb/source/Host/posix/ProcessLauncherPosixFork.cpp
@@ -14,6 +14,7 @@
 #include "lldb/Utility/FileSpec.h"
 #include "lldb/Utility/Log.h"
 #include "llvm/Support/Errno.h"
+#include "llvm/Support/FileSystem.h"
 
 #include <climits>
 #include <sys/ptrace.h>
@@ -143,9 +144,32 @@ static void DupDescriptor(int error_fd, const FileSpec &file_spec, int fd,
     // Close everything besides stdin, stdout, and stderr that has no file
     // action to avoid leaking. Only do this when debugging, as elsewhere we
     // actually rely on passing open descriptors to child processes.
-    for (int fd = 3; fd < sysconf(_SC_OPEN_MAX); ++fd)
-      if (!info.GetFileActionForFD(fd) && fd != error_fd)
-        close(fd);
+
+    const llvm::StringRef proc_fd_path = "/proc/self/fd";
+    std::error_code ec;
+    bool result;
+    ec = llvm::sys::fs::is_directory(proc_fd_path, result);
+    if (result) {
+      std::vector<int> files_to_close;
+      // Directory iterator doesn't ensure any sequence.
+      for (llvm::sys::fs::directory_iterator iter(proc_fd_path, ec), file_end;
+           iter != file_end && !ec; iter.increment(ec)) {
+        int fd = std::stoi(iter->path().substr(proc_fd_path.size() + 1));
+
+        // Don't close first three entries since they are stdin, stdout and
+        // stderr.
+        if (fd > 2 && !info.GetFileActionForFD(fd) && fd != error_fd)
+          files_to_close.push_back(fd);
+      }
+      for (int file_to_close : files_to_close)
+        close(file_to_close);
+    } else {
+      // Since /proc/self/fd didn't work, trying the slow way instead.
+      int max_fd = sysconf(_SC_OPEN_MAX);
+      for (int fd = 3; fd < max_fd; ++fd)
+        if (!info.GetFileActionForFD(fd) && fd != error_fd)
+          close(fd);
+    }
 
     // Start tracing this child that is about to exec.
     if (ptrace(PT_TRACE_ME, 0, nullptr, 0) == -1)