* io.c (rb_io_initialize): check if the descriptor can be accessed

  in the specified open mode.  [ruby-dev:38571]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24102 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 17 insertions, 5 deletions

diff --git a/io.c b/io.c
index 45c4a73215..4e576e710e 100644
--- a/io.c
+++ b/io.c
@@ -6342,7 +6342,11 @@ rb_io_initialize(int argc, VALUE *argv, VALUE io)
     int fd, fmode, oflags = O_RDONLY;
     convconfig_t convconfig;
     VALUE opt;
+#if defined(HAVE_FCNTL) && defined(F_GETFL)
+    int ofmode;
+#else
     struct stat st;
+#endif
 
     rb_secure(4);
 
@@ -6351,15 +6355,23 @@ rb_io_initialize(int argc, VALUE *argv, VALUE io)
     rb_io_extract_modeenc(&vmode, 0, opt, &oflags, &fmode, &convconfig);
 
     fd = NUM2INT(fnum);
+#if defined(HAVE_FCNTL) && defined(F_GETFL)
+    oflags = fcntl(fd, F_GETFL);
+    if (oflags == -1) rb_sys_fail(0);
+#else
     if (fstat(fd, &st) == -1) rb_sys_fail(0);
+#endif
     UPDATE_MAXFD(fd);
-    if (NIL_P(vmode)) {
 #if defined(HAVE_FCNTL) && defined(F_GETFL)
-        oflags = fcntl(fd, F_GETFL);
-        if (oflags == -1) rb_sys_fail(0);
-        fmode = rb_io_oflags_fmode(oflags);
-#endif
+    ofmode = rb_io_oflags_fmode(oflags);
+    if (NIL_P(vmode)) {
+	fmode = ofmode;
+    }
+    else if ((~ofmode & fmode) & FMODE_READWRITE) {
+	VALUE error = INT2FIX(EINVAL);
+	rb_exc_raise(rb_class_new_instance(1, &error, rb_eSystemCallError));
     }
+#endif
     MakeOpenFile(io, fp);
     fp->fd = fd;
     fp->mode = fmode;