view_compiler.cpp: clean up file descriptor handling

For file descriptors which are explicitly passed across an exec()
boundary, mark them as // NOLINT(android-cloexec-open). This suppresses
clang-tidy link checks (intended to be added as part of b/129350825)

Don't call close(STDOUT_FILENO). The dup2() syscall atomically closes
this for us, so we don't need to do it ourselves. Additionally, this
also fixes a race condition where another thread may call open() and get
an FD corresponding to STDOUT_FILENO, which we will then close as part
of the dup2() call. Removing the close() makes file descriptor handling
atomic.

Set O_CLOEXEC on outfd. The pre-duped file descriptor should have
O_CLOEXEC set on it. Calling dup2() will dup the file descriptor, but
NOT preserve the O_CLOEXEC flag. Quoting "man dup2":

  The two file descriptors do not share file descriptor flags
  (the close-on-exec flag).  The close-on-exec flag (FD_CLOEXEC;
  see fcntl(2)) for the duplicate descriptor is off.

If we don't set the O_CLOEXEC flag on outfd, we'll be leaking the file
descriptor twice, once as STDOUT_FILENO, and once as outfd. The second
leak is undesirable although harmless.

Additional cleanup: Add missing newlines at end of file.

Bug: 129350825
Test: compiles
Change-Id: Ic83ad72ef8a38106ad95ec0202c5c09c61fcf3e7

2 files changed, 4 insertions, 8 deletions

diff --git a/cmds/installd/view_compiler.cpp b/cmds/installd/view_compiler.cpp
index f1ac7178f6..60d6492e70 100644
--- a/cmds/installd/view_compiler.cpp
+++ b/cmds/installd/view_compiler.cpp
@@ -45,7 +45,7 @@ bool view_compiler(const char* apk_path, const char* package_name, const char* o
     // and pass file descriptors.
 
     // Open input file
-    unique_fd infd{open(apk_path, 0)};
+    unique_fd infd{open(apk_path, O_RDONLY)}; // NOLINT(android-cloexec-open)
     if (infd.get() < 0) {
         PLOG(ERROR) << "Could not open input file: " << apk_path;
         return false;
@@ -53,7 +53,7 @@ bool view_compiler(const char* apk_path, const char* package_name, const char* o
 
     // Set up output file. viewcompiler can't open outputs by fd, but it can write to stdout, so
     // we close stdout and open it towards the right output.
-    unique_fd outfd{open(out_dex_file, O_CREAT | O_TRUNC | O_WRONLY, 0644)};
+    unique_fd outfd{open(out_dex_file, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC, 0644)};
     if (outfd.get() < 0) {
         PLOG(ERROR) << "Could not open output file: " << out_dex_file;
         return false;
@@ -62,10 +62,6 @@ bool view_compiler(const char* apk_path, const char* package_name, const char* o
         PLOG(ERROR) << "Could not change output file permissions";
         return false;
     }
-    if (close(STDOUT_FILENO) != 0) {
-        PLOG(ERROR) << "Could not close stdout";
-        return false;
-    }
     if (dup2(outfd, STDOUT_FILENO) < 0) {
         PLOG(ERROR) << "Could not duplicate output file descriptor";
         return false;
@@ -96,4 +92,4 @@ bool view_compiler(const char* apk_path, const char* package_name, const char* o
 }
 
 } // namespace installd
-} // namespace android
\ No newline at end of file
+} // namespace android
diff --git a/cmds/installd/view_compiler.h b/cmds/installd/view_compiler.h
index f7c6e57722..aa141ca257 100644
--- a/cmds/installd/view_compiler.h
+++ b/cmds/installd/view_compiler.h
@@ -26,4 +26,4 @@ bool view_compiler(const char* apk_path, const char* package_name, const char* o
 } // namespace installd
 } // namespace android
 
-#endif // VIEW_COMPILER_H_
\ No newline at end of file
+#endif // VIEW_COMPILER_H_