From: Eli Zaretskii <eliz@gnu.org>
Date: Wed, 22 May 2024 11:10:53 +0000 (+0300)
Subject: Avoid crashes on MS-Windows due to invalid UNC file names
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=b98ed825080df50e50b528a4b372e78c4f9a1f83;p=emacs.git

Avoid crashes on MS-Windows due to invalid UNC file names

* src/w32.c (parse_root): Avoid crashes due to invalid (too short)
UNC names, such as "\\".  (Bug#70914)

* test/src/fileio-tests.el (fileio-tests-invalid-UNC): New test.

(cherry picked from commit 350ae75f5c1c47a03560e43e8699781c04c9078a)
---

diff --git a/src/w32.c b/src/w32.c
index d34ab70f82d..a1b34e4103b 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -2572,7 +2572,7 @@ parse_root (const char * name, const char ** pPath)
       name += 2;
       do
         {
-	  if (IS_DIRECTORY_SEP (*name) && --slashes == 0)
+	  if (!*name || (IS_DIRECTORY_SEP (*name) && --slashes == 0))
 	    break;
 	  name++;
 	}
diff --git a/test/src/fileio-tests.el b/test/src/fileio-tests.el
index 81eef37b903..750de8444c9 100644
--- a/test/src/fileio-tests.el
+++ b/test/src/fileio-tests.el
@@ -217,4 +217,10 @@ Also check that an encoding error can appear in a symlink."
     (should (equal (expand-file-name file nil) file))
     (file-name-case-insensitive-p file)))
 
+(ert-deftest fileio-tests-invalid-UNC ()
+  (skip-unless (eq system-type 'windows-nt))
+  ;; These should not crash, see bug#70914.
+  (should-not (file-exists-p "//"))
+  (should (file-attributes "//")))
+
 ;;; fileio-tests.el ends here