[newlib-cygwin] Cygwin: symlinks: fix WSL symlink creation if cygdrive prefix is /

[newlib-cygwin] Cygwin: symlinks: fix WSL symlink creation if cygdrive prefix is /

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=6b97962073097adb7efe6ac04265df6a8596af21

commit 6b97962073097adb7efe6ac04265df6a8596af21
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Tue Apr 21 10:31:53 2020 +0200

    Cygwin: symlinks: fix WSL symlink creation if cygdrive prefix is /
    
    If the cygdrive prefix is /, then the following happens right now:
    
      $ ln -s /tmp/foo .
      $ ls -l foo
      lrwxrwxrwx 1 user group 12 Apr 15 23:44 foo -> /mnt/tmp/foo
    
    Fix this by skipping cygdrive prefix conversion to WSL drive
    prefix "/mnt", if the cygdrive prefix is just "/".  There's no
    satisfying way to do the right thing all the time in this case
    anyway.  For a description and the alternatives, see
    https://cygwin.com/pipermail/cygwin-developers/2020-April/011859.html
    
    Also, fix a typo in a comment.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/path.cc | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index f2b5cdbf1..36aa8278f 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -1886,15 +1886,17 @@ symlink_wsl (const char *oldpath, path_conv &win32_newpath)
   rpl->ReparseTag = IO_REPARSE_TAG_LX_SYMLINK;
   rpl->Reserved = 0;
   rpl->LxSymlinkReparseBuffer.FileType = 2;
-  /* Convert cygdrive prefix to "/mnt" for WSL compatibility. */
-  if (path_prefix_p (mount_table->cygdrive, oldpath,
-		     mount_table->cygdrive_len, false))
+  /* Convert cygdrive prefix to "/mnt" for WSL compatibility, but only if
+     cygdrive prefix is not "/", otherwise suffer random "/mnt" symlinks... */
+  if (mount_table->cygdrive_len > 1
+      && path_prefix_p (mount_table->cygdrive, oldpath,
+			mount_table->cygdrive_len, false))
     stpcpy (stpcpy (path_buf, "/mnt"),
 	    oldpath + mount_table->cygdrive_len - 1);
   else
     *stpncpy (path_buf, oldpath, max_pathlen) = '\0';
   /* Convert target path to UTF-16 and then back to UTF-8 to make sure the
-     WSL symlink is in UTF-8, independet of the current Cygwin codeset. */
+     WSL symlink is in UTF-8, independent of the current Cygwin codeset. */
   sys_mbstowcs (utf16, NT_MAX_PATH, path_buf);
   len = WideCharToMultiByte (CP_UTF8, 0, utf16, -1, path_buf, max_pathlen,
 			     NULL, NULL);