From b2e1ec0199f709df9bf62327dcb503f285eeb707 Mon Sep 17 00:00:00 2001
From: Arfrever Frehtes Taifersar Arahesis <Arfrever@Apache.Org>
Date: Tue, 23 Jul 2019 08:23:51 +0200
Subject: [PATCH] dblink._collision_protect: Detect internal collisions.

Implement detection of internal collisions (between files of the same package,
located in separate directories in the installation image (${D}) corresponding
to merged directories in the target filesystem (${ROOT})).

This provides protection against overwriting some files when performing merging
of files from ${D} to ${ROOT} in some filesystem layouts (such as /-merged layout
or /usr-merged layout).

Automatically resolve collision between symbolic link and its target
by dropping symbolic link.

Bug: https://bugs.gentoo.org/690484
Signed-off-by: Arfrever Frehtes Taifersar Arahesis <Arfrever@Apache.Org>
---
 lib/portage/dbapi/vartree.py | 65 +++++++++++++++++++++++++++++++++---
 1 file changed, 61 insertions(+), 4 deletions(-)

diff --git a/lib/portage/dbapi/vartree.py b/lib/portage/dbapi/vartree.py
index e2fce7736..1d2496249 100644
--- a/lib/portage/dbapi/vartree.py
+++ b/lib/portage/dbapi/vartree.py
@@ -3418,6 +3418,8 @@ class dblink(object):
 
 			os = _os_merge
 
+			real_relative_paths = {}
+
 			collision_ignore = []
 			for x in portage.util.shlex_split(
 				self.settings.get("COLLISION_IGNORE", "")):
@@ -3469,8 +3471,35 @@ class dblink(object):
 					previous = current
 					progress_shown = True
 
-				dest_path = normalize_path(
-					os.path.join(destroot, f.lstrip(os.path.sep)))
+				src_path = normalize_path(os.path.join(srcroot, f.lstrip(os.path.sep)))
+				dest_path = normalize_path(os.path.join(destroot, f.lstrip(os.path.sep)))
+
+				# Relative path with symbolic links resolved only in parent directories
+				real_relative_path = os.path.join(os.path.realpath(os.path.dirname(dest_path)), os.path.basename(dest_path))[len(destroot):]
+
+				# Automatic resolution of selected types of internal collisions
+				src_file_deleted = False
+				for other_colliding_file in real_relative_paths.get(real_relative_path, []):
+					if src_file_deleted:
+						break
+					if f_type == "sym":
+						# When symbolic link collides with its target, then
+						# this symbolic link is dropped.
+						symlink_target = _unicode_decode(_os.readlink(_unicode_encode(src_path,
+							encoding=_encodings["merge"], errors="strict")),
+							encoding=_encodings["merge"], errors="replace")
+						if os.path.isabs(symlink_target):
+							if normalize_path(symlink_target.lstrip(os.path.sep)) == other_colliding_file:
+								os.unlink(src_path)
+								src_file_deleted = True
+						else:
+							if normalize_path(os.path.join(parent, symlink_target).lstrip(os.path.sep)) == other_colliding_file:
+								os.unlink(src_path)
+								src_file_deleted = True
+				if src_file_deleted:
+					continue
+
+				real_relative_paths.setdefault(real_relative_path, []).append(f.lstrip(os.path.sep))
 
 				parent = os.path.dirname(dest_path)
 				if parent not in dirs:
@@ -3556,9 +3585,16 @@ class dblink(object):
 							break
 					if stopmerge:
 						collisions.append(f)
+
+			internal_collisions = {}
+			for k, v in real_relative_paths.items():
+				if len(v) >= 2:
+					internal_collisions[k] = v
+
 			if progress_shown:
 				showMessage(_("100% done\n"))
-			return collisions, dirs_ro, symlink_collisions, plib_collisions
+
+			return collisions, internal_collisions, dirs_ro, symlink_collisions, plib_collisions
 
 	def _lstat_inode_map(self, path_iter):
 		"""
@@ -4081,7 +4117,7 @@ class dblink(object):
 			if blocker.exists():
 				blockers.append(blocker)
 
-		collisions, dirs_ro, symlink_collisions, plib_collisions = \
+		collisions, internal_collisions, dirs_ro, symlink_collisions, plib_collisions = \
 			self._collision_protect(srcroot, destroot,
 			others_in_slot + blockers, filelist, linklist)
 
@@ -4109,6 +4145,27 @@ class dblink(object):
 			eerror(msg)
 			return 1
 
+		if internal_collisions:
+			msg = _("Package '%s' has internal collisions (between files "
+				"in separate directories in the installation image (${D}) "
+				"corresponding to merged directories in the target "
+				"filesystem (${ROOT})):") % self.settings.mycpv
+			msg = textwrap.wrap(msg, 70)
+			msg.append("")
+			for k, v in sorted(internal_collisions.items()):
+				msg.append("\t%s" % os.path.join(destroot, k.lstrip(os.path.sep)))
+				for f in sorted(v):
+					msg.append("\t\t%s" % os.path.join(destroot, f.lstrip(os.path.sep)))
+				msg.append("")
+			self._elog("eerror", "preinst", msg)
+
+			msg = _("Package '%s' NOT merged due to internal collisions.") % \
+				self.settings.mycpv
+			msg += _(" If necessary, refer to your elog messages for the whole "
+				"content of the above message.")
+			eerror(textwrap.wrap(msg, 70))
+			return 1
+
 		if symlink_collisions:
 			# Symlink collisions need to be distinguished from other types
 			# of collisions, in order to avoid confusion (see bug #409359).
-- 
2.22.0