[newlib-cygwin] Cygwin: normalize_posix_path: fix error handling when .. is encountered

[Ken Brown]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=4aefad2bb827afa273fcd768bd06dd618d41ae75

commit 4aefad2bb827afa273fcd768bd06dd618d41ae75
Author: Ken Brown <kbrown@cornell.edu>
Date:   Wed Jan 20 10:12:58 2021 -0500

    Cygwin: normalize_posix_path: fix error handling when .. is encountered
    
    When .. is in the source path and the path prefix exists but is not a
    directory, return ENOTDIR instead of ENOENT.  This fixes a POSIX
    compliance issue for realpath(3):
    
      https://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html
    
    Addresses: https://lists.gnu.org/archive/html/bug-gnulib/2021-01/msg00214.html

Diff:
---
 winsup/cygwin/path.cc       | 4 +++-
 winsup/cygwin/release/3.2.0 | 4 ++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index abd3687df..6dc162806 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -323,8 +323,10 @@ normalize_posix_path (const char *src, char *dst, char *&tail)
 			  if (!tp.check_usage (4, 3))
 			    return ELOOP;
 			  path_conv head (dst, PC_SYM_FOLLOW | PC_POSIX);
-			  if (!head.isdir())
+			  if (!head.exists ())
 			    return ENOENT;
+			  if (!head.isdir ())
+			    return ENOTDIR;
 			  /* At this point, dst is a normalized path.  If the
 			     normalized path created by path_conv does not
 			     match the normalized path we're just testing, then
diff --git a/winsup/cygwin/release/3.2.0 b/winsup/cygwin/release/3.2.0
index c18a848de..43725cec2 100644
--- a/winsup/cygwin/release/3.2.0
+++ b/winsup/cygwin/release/3.2.0
@@ -48,3 +48,7 @@ Bug Fixes
 
 - Fix a bug in fstatat(2) on 32 bit that could cause it to return garbage.
   Addresses: https://cygwin.com/pipermail/cygwin/2021-January/247399.html
+
+- Fix the errno when a path contains .. and the prefix exists but is
+  not a directory.
+  Addresses: https://lists.gnu.org/archive/html/bug-gnulib/2021-01/msg00214.html