From 063c757570f0c11678e9ade47811c3daeba26233 Mon Sep 17 00:00:00 2001
From: Thomas Adamcik <thomas@adamcik.no>
Date: Wed, 15 Oct 2014 23:21:11 +0200
Subject: [PATCH] utils/path: Add support for handling sym/hardlink loops

---
 mopidy/utils/path.py     | 15 +++++++++++----
 tests/utils/test_path.py | 39 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/mopidy/utils/path.py b/mopidy/utils/path.py
index 34a7f75e..01b97a50 100644
--- a/mopidy/utils/path.py
+++ b/mopidy/utils/path.py
@@ -122,7 +122,7 @@ def _find_worker(relative, follow, done, work, results, errors):
     """
     while not done.is_set():
         try:
-            entry = work.get(block=False)
+            entry, parents = work.get(block=False)
         except queue.Empty:
             continue
 
@@ -137,13 +137,19 @@ def _find_worker(relative, follow, done, work, results, errors):
             else:
                 st = os.lstat(entry)
 
+            if (st.st_dev, st.st_ino) in parents:
+                errors[path] = Exception('Sym/hardlink loop found.')
+                continue
+
+            parents = parents + [(st.st_dev, st.st_ino)]
             if stat.S_ISDIR(st.st_mode):
                 for e in os.listdir(entry):
-                    work.put(os.path.join(entry, e))
+                    work.put((os.path.join(entry, e), parents))
             elif stat.S_ISREG(st.st_mode):
                 results[path] = st
             else:
                 errors[path] = Exception('Not a file or directory')
+
         except os.error as e:
             errors[path] = e
         finally:
@@ -153,7 +159,8 @@ def _find_worker(relative, follow, done, work, results, errors):
 def _find(root, thread_count=10, relative=False, follow=False):
     """Threaded find implementation that provides stat results for files.
 
-    Note that we do _not_ handle loops from bad sym/hardlinks in any way.
+    Tries to protect against sym/hardlink loops by keeping an eye on parent
+    (st_dev, st_ino) pairs.
 
     :param str root: root directory to search from, may not be a file
     :param int thread_count: number of workers to use, mainly useful to
@@ -166,7 +173,7 @@ def _find(root, thread_count=10, relative=False, follow=False):
     errors = {}
     done = threading.Event()
     work = queue.Queue()
-    work.put(os.path.abspath(root))
+    work.put((os.path.abspath(root), []))
 
     if not relative:
         root = None
diff --git a/tests/utils/test_path.py b/tests/utils/test_path.py
index 0e91e008..8dafd951 100644
--- a/tests/utils/test_path.py
+++ b/tests/utils/test_path.py
@@ -221,12 +221,12 @@ class FindMTimesTest(unittest.TestCase):
         shutil.rmtree(self.tmpdir, ignore_errors=True)
 
     def mkdir(self, *args):
-        name = os.path.join(self.tmpdir, *args)
+        name = os.path.join(self.tmpdir, *[bytes(a) for a in args])
         os.mkdir(name)
         return name
 
     def touch(self, *args):
-        name = os.path.join(self.tmpdir, *args)
+        name = os.path.join(self.tmpdir, *[bytes(a) for a in args])
         open(name, 'w').close()
         return name
 
@@ -320,6 +320,7 @@ class FindMTimesTest(unittest.TestCase):
         pass
 
     def test_symlink_pointing_at_itself_fails(self):
+        """Symlink pointing at itself should give as an OS error"""
         link = os.path.join(self.tmpdir, 'link')
         os.symlink(link, link)
 
@@ -328,12 +329,44 @@ class FindMTimesTest(unittest.TestCase):
         self.assertEqual({link: tests.IsA(OSError)}, errors)
 
     def test_symlink_pointing_at_parent_fails(self):
+        """We should detect a loop via the parent and give up on the branch"""
         os.symlink(self.tmpdir, os.path.join(self.tmpdir, 'link'))
 
         result, errors = path.find_mtimes(self.tmpdir, follow=True)
         self.assertEqual({}, result)
         self.assertEqual(1, len(errors))
-        self.assertEqual(tests.IsA(OSError), errors.values()[0])
+        self.assertEqual(tests.IsA(Exception), errors.values()[0])
+
+    def test_indirect_symlink_loop(self):
+        """More indirect loops should also be detected"""
+        # Setup tmpdir/directory/loop where loop points to tmpdir
+        directory = os.path.join(self.tmpdir, b'directory')
+        loop = os.path.join(directory, b'loop')
+
+        os.mkdir(directory)
+        os.symlink(self.tmpdir, loop)
+
+        result, errors = path.find_mtimes(self.tmpdir, follow=True)
+        self.assertEqual({}, result)
+        self.assertEqual({loop: tests.IsA(Exception)}, errors)
+
+    def test_symlink_branches_are_not_excluded(self):
+        """Using symlinks to make a file show up multiple times should work"""
+        self.mkdir('directory')
+        target = self.touch('directory', 'target')
+        link1 = os.path.join(self.tmpdir, b'link1')
+        link2 = os.path.join(self.tmpdir, b'link2')
+
+        os.symlink(target, link1)
+        os.symlink(target, link2)
+
+        expected = {target: tests.any_int,
+                    link1: tests.any_int,
+                    link2: tests.any_int}
+
+        result, errors = path.find_mtimes(self.tmpdir, follow=True)
+        self.assertEqual(expected, result)
+        self.assertEqual({}, errors)
 
 
 # TODO: kill this in favour of just os.path.getmtime + mocks