[PATCH] Cygwin: exec: check execute bit prior to evaluating script

[Corinna Vinschen <corinna at vinschen dot de>]

From: Corinna Vinschen <corinna-cygwin@cygwin.com>

When the exec family of functions is called for a script-like
file, the av::setup function handles the exec[vl]p case as
well.  The execve case for files not starting with a she-bang
is handled first by returning ENOEXEC.  Only after that, the
file's executability is checked.

This leads to the problem that ENOEXEC is returned for non-executable
files as well.  A calling shell interprets this as a file it should try
to run as script.  This is not desired for non-executable files.

Fix this problem by checking the file for executability first.  Only
after that, follow the other potential code paths.
---
 winsup/cygwin/spawn.cc | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
index 7f7af4449da1..d95772802f8f 100644
--- a/winsup/cygwin/spawn.cc
+++ b/winsup/cygwin/spawn.cc
@@ -1172,6 +1172,12 @@ av::setup (const char *prog_arg, path_conv& real_path, const char *ext,
 	  }
 	UnmapViewOfFile (buf);
   just_shell:
+	/* Check if script is executable.  Otherwise we start non-executable
+	   scripts successfully, which is incorrect behaviour. */
+	if (real_path.has_acls ()
+	    && check_file_access (real_path, X_OK, true) < 0)
+	  return -1;	/* errno is already set. */
+
 	if (!pgm)
 	  {
 	    if (!p_type_exec)
@@ -1188,12 +1194,6 @@ av::setup (const char *prog_arg, path_conv& real_path, const char *ext,
 	    arg1 = NULL;
 	  }
 
-	/* Check if script is executable.  Otherwise we start non-executable
-	   scripts successfully, which is incorrect behaviour. */
-	if (real_path.has_acls ()
-	    && check_file_access (real_path, X_OK, true) < 0)
-	  return -1;	/* errno is already set. */
-
 	/* Replace argv[0] with the full path to the script if this is the
 	   first time through the loop. */
 	replace0_maybe (prog_arg);
-- 
2.20.1