Handle removal of empty directories properly

This addresses FS#25141. We shouldn't remove every empty directory we
come across during the removal process unless it is truly not known to
any other package. This will prevent removal of essential directories
such as '/var/lock/'.

This is accomplished by first checking the empty/non-empty status of a
directory, which was previously done implicitly by calling rmdir() and
ignoring errors. We do this to avoid the next (new) check in most cases,
which is to look at all local packages to see if the to-be-removed
directory is present in another packages' filelist. If we do not find it
anywhere, then we remove it, else we keep the file around.

The pactest has been updated to test more cases, as well as finding a
flaw in the original expected to fail case- we need separate DIR and
FILE based EXIST rules.

Signed-off-by: Dan McGee <dan@archlinux.org>

3 files changed, 82 insertions, 6 deletions

diff --git a/lib/libalpm/remove.c b/lib/libalpm/remove.c
index b15dbaa5..c2a8ad2c 100644
--- a/lib/libalpm/remove.c
+++ b/lib/libalpm/remove.c
@@ -232,8 +232,8 @@ static void unlink_file(alpm_handle_t *handle, alpm_pkg_t *info,
 	 * see the big comment block in db_find_fileconflicts() for an
 	 * explanation. */
 	if(alpm_list_find_str(skip_remove, fileobj->name)) {
-		_alpm_log(handle, ALPM_LOG_DEBUG, "%s is in skip_remove, skipping removal\n",
-				file);
+		_alpm_log(handle, ALPM_LOG_DEBUG,
+				"%s is in skip_remove, skipping removal\n", file);
 		return;
 	}
 
@@ -247,11 +247,44 @@ static void unlink_file(alpm_handle_t *handle, alpm_pkg_t *info,
 	}
 
 	if(S_ISDIR(buf.st_mode)) {
-		if(rmdir(file)) {
-			/* this is okay, other packages are probably using it (like /usr) */
-			_alpm_log(handle, ALPM_LOG_DEBUG, "keeping directory %s\n", file);
+		ssize_t files = _alpm_files_in_directory(handle, file, 0);
+		/* if we have files, no need to remove the directory */
+		if(files > 0) {
+			_alpm_log(handle, ALPM_LOG_DEBUG, "keeping directory %s (contains files)\n",
+					file);
+		} else if(files < 0) {
+			_alpm_log(handle, ALPM_LOG_DEBUG,
+					"keeping directory %s (could not count files)\n", file);
 		} else {
-			_alpm_log(handle, ALPM_LOG_DEBUG, "removing directory %s\n", file);
+			/* one last check- does any other package own this file? */
+			alpm_list_t *local, *local_pkgs;
+			int found = 0;
+			local_pkgs = _alpm_db_get_pkgcache(handle->db_local);
+			for(local = local_pkgs; local && !found; local = local->next) {
+				alpm_pkg_t *local_pkg = local->data;
+				alpm_list_t *files;
+
+				/* we duplicated the package when we put it in the removal list, so we
+				 * so we can't use direct pointer comparison here. */
+				if(_alpm_pkg_cmp(info, local_pkg) == 0) {
+					continue;
+				}
+				files = alpm_pkg_get_files(local_pkg);
+				if(_alpm_filelist_contains(files, fileobj->name)) {
+					_alpm_log(handle, ALPM_LOG_DEBUG,
+							"keeping directory %s (owned by %s)\n", file, local_pkg->name);
+					found = 1;
+				}
+			}
+			if(!found) {
+				if(rmdir(file)) {
+					_alpm_log(handle, ALPM_LOG_DEBUG,
+							"directory removal of %s failed: %s\n", file, strerror(errno));
+				} else {
+					_alpm_log(handle, ALPM_LOG_DEBUG,
+							"removed directory %s (no remaining owners)\n", file);
+				}
+			}
 		}
 	} else {
 		/* if the file needs backup and has been modified, back it up to .pacsave */
diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c
index cd7f19c9..62313d81 100644
--- a/lib/libalpm/util.c
+++ b/lib/libalpm/util.c
@@ -388,6 +388,48 @@ int _alpm_rmrf(const char *path)
 	return 0;
 }
 
+/**
+ * Determine if there are files in a directory
+ * @param handle the context handle
+ * @param path the full absolute directory path
+ * @param full_count whether to return an exact count of files
+ * @return a file count if full_count is != 0, else >0 if directory has
+ * contents, 0 if no contents, and -1 on error
+ */
+ssize_t _alpm_files_in_directory(alpm_handle_t *handle, const char *path,
+		int full_count)
+{
+	ssize_t files = 0;
+	struct dirent *ent;
+	DIR *dir = opendir(path);
+
+	if(!dir) {
+		if(errno == ENOTDIR) {
+			_alpm_log(handle, ALPM_LOG_DEBUG, "%s was not a directory\n", path);
+		} else {
+			_alpm_log(handle, ALPM_LOG_DEBUG, "could not read directory %s\n",
+					path);
+		}
+		return -1;
+	}
+	while((ent = readdir(dir)) != NULL) {
+		const char *name = ent->d_name;
+
+		if(strcmp(name, ".") == 0 || strcmp(name, "..") == 0) {
+			continue;
+		}
+
+		files++;
+
+		if(!full_count) {
+			break;
+		}
+	}
+
+	closedir(dir);
+	return files;
+}
+
 int _alpm_logaction(alpm_handle_t *handle, const char *fmt, va_list args)
 {
 	int ret = 0;
diff --git a/lib/libalpm/util.h b/lib/libalpm/util.h
index 450dac9b..d66ddee9 100644
--- a/lib/libalpm/util.h
+++ b/lib/libalpm/util.h
@@ -100,6 +100,7 @@ int _alpm_unpack_single(alpm_handle_t *handle, const char *archive,
 int _alpm_unpack(alpm_handle_t *handle, const char *archive, const char *prefix,
 		alpm_list_t *list, int breakfirst);
 int _alpm_rmrf(const char *path);
+ssize_t _alpm_files_in_directory(alpm_handle_t *handle, const char *path, int full_count);
 int _alpm_logaction(alpm_handle_t *handle, const char *fmt, va_list args);
 int _alpm_run_chroot(alpm_handle_t *handle, const char *path, char *const argv[]);
 int _alpm_ldconfig(alpm_handle_t *handle);