support: Prevent multiple deletion of temporary files

Otherwise, another user might recreate these files after the first
deletion.  Particularly with temporary directories, this could result
in the removal of unintended files through symbol link attacks.

1 files changed, 18 insertions, 32 deletions

diff --git a/posix/tst-exec.c b/posix/tst-exec.c
index be0114e..12a0f57 100644
--- a/posix/tst-exec.c
+++ b/posix/tst-exec.c
@@ -47,6 +47,10 @@ extern int do_test (int argc, char *argv[]);
 static char *name1;
 static char *name2;
 
+/* File descriptors for these temporary files.  */
+static int temp_fd1 = -1;
+static int temp_fd2 = -1;
+
 /* The contents of our files.  */
 static const char fd1string[] = "This file should get closed";
 static const char fd2string[] = "This file should stay opened";
@@ -56,18 +60,14 @@ static const char fd2string[] = "This file should stay opened";
 void
 do_prepare (int argc, char *argv[])
 {
-   size_t name_len;
-
-   name_len = strlen (test_dir);
-   name1 = xmalloc (name_len + sizeof ("/execXXXXXX"));
-   mempcpy (mempcpy (name1, test_dir, name_len),
-	    "/execXXXXXX", sizeof ("/execXXXXXX"));
-   add_temp_file (name1);
-
-   name2 = xmalloc (name_len + sizeof ("/execXXXXXX"));
-   mempcpy (mempcpy (name2, test_dir, name_len),
-	    "/execXXXXXX", sizeof ("/execXXXXXX"));
-   add_temp_file (name2);
+  /* We must not open any files in the restart case.  */
+  if (restart)
+    return;
+
+  temp_fd1 = create_temp_file ("exec", &name1);
+  temp_fd2 = create_temp_file ("exec", &name2);
+  if (temp_fd1 < 0 || temp_fd2 < 0)
+    exit (1);
 }
 
 
@@ -120,8 +120,6 @@ int
 do_test (int argc, char *argv[])
 {
   pid_t pid;
-  int fd1;
-  int fd2;
   int flags;
   int status;
 
@@ -151,26 +149,18 @@ do_test (int argc, char *argv[])
   /* Prepare the test.  We are creating two files: one which file descriptor
      will be marked with FD_CLOEXEC, another which is not.  */
 
-   /* Open our test files.   */
-   fd1 = mkstemp (name1);
-   if (fd1 == -1)
-     error (EXIT_FAILURE, errno, "cannot open test file `%s'", name1);
-   fd2 = mkstemp (name2);
-   if (fd2 == -1)
-     error (EXIT_FAILURE, errno, "cannot open test file `%s'", name2);
-
    /* Set the bit.  */
-   flags = fcntl (fd1, F_GETFD, 0);
+   flags = fcntl (temp_fd1, F_GETFD, 0);
    if (flags < 0)
      error (EXIT_FAILURE, errno, "cannot get flags");
    flags |= FD_CLOEXEC;
-   if (fcntl (fd1, F_SETFD, flags) < 0)
+   if (fcntl (temp_fd1, F_SETFD, flags) < 0)
      error (EXIT_FAILURE, errno, "cannot set flags");
 
    /* Write something in the files.  */
-   if (write (fd1, fd1string, strlen (fd1string)) != strlen (fd1string))
+   if (write (temp_fd1, fd1string, strlen (fd1string)) != strlen (fd1string))
      error (EXIT_FAILURE, errno, "cannot write to first file");
-   if (write (fd2, fd2string, strlen (fd2string)) != strlen (fd2string))
+   if (write (temp_fd2, fd2string, strlen (fd2string)) != strlen (fd2string))
      error (EXIT_FAILURE, errno, "cannot write to second file");
 
   /* We want to test the `exec' function.  To do this we restart the program
@@ -181,8 +171,8 @@ do_test (int argc, char *argv[])
       char fd1name[18];
       char fd2name[18];
 
-      snprintf (fd1name, sizeof fd1name, "%d", fd1);
-      snprintf (fd2name, sizeof fd2name, "%d", fd2);
+      snprintf (fd1name, sizeof fd1name, "%d", temp_fd1);
+      snprintf (fd2name, sizeof fd2name, "%d", temp_fd2);
 
       /* This is the child.  Construct the command line.  */
       if (argc == 5)
@@ -205,9 +195,5 @@ do_test (int argc, char *argv[])
     error (EXIT_FAILURE, 0, "Child terminated incorrectly");
   status = WEXITSTATUS (status);
 
-  /* Remove the test files.  */
-  unlink (name1);
-  unlink (name2);
-
   return status;
 }