[PATCH] Cygwin: rmdir: fail if last component is a symlink, as on Linux

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[PATCH] Cygwin: rmdir: fail if last component is a symlink, as on Linux

Ken Brown-6
If the last component of the directory name is a symlink followed by a
slash, rmdir should fail, even if the symlink resolves to an existing
empty directory.

mkdir was similarly fixed in 2009 in commit
52dba6a5c45e8d8ba1e237a15213311dc11d91fb.  Modify a comment to clarify
the purpose of that commit.

Addresses https://cygwin.com/ml/cygwin/2019-09/msg00221.html.
---
 winsup/cygwin/dir.cc | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/dir.cc b/winsup/cygwin/dir.cc
index b757851d5..f65c9bdad 100644
--- a/winsup/cygwin/dir.cc
+++ b/winsup/cygwin/dir.cc
@@ -305,15 +305,14 @@ mkdir (const char *dir, mode_t mode)
 
   __try
     {
-      /* POSIX says mkdir("symlink-to-missing/") should create the
- directory "missing", but Linux rejects it with EEXIST.  Copy
- Linux behavior for now.  */
-
       if (!*dir)
  {
   set_errno (ENOENT);
   __leave;
  }
+      /* Following Linux, do not resolve the last component of DIR if
+ it is a symlink, even if DIR has a trailing slash.  Achieve
+ this by stripping trailing slashes or backslashes.  */
       if (isdirsep (dir[strlen (dir) - 1]))
  {
   /* This converts // to /, but since both give EEXIST, we're okay.  */
@@ -354,6 +353,25 @@ rmdir (const char *dir)
 
   __try
     {
+      if (!*dir)
+ {
+  set_errno (ENOENT);
+  __leave;
+ }
+
+      /* Following Linux, do not resolve the last component of DIR if
+ it is a symlink, even if DIR has a trailing slash.  Achieve
+ this by stripping trailing slashes or backslashes.  */
+      if (isdirsep (dir[strlen (dir) - 1]))
+ {
+  /* This converts // to /, but since both give ENOTEMPTY,
+     we're okay.  */
+  char *buf;
+  char *p = stpcpy (buf = tp.c_get (), dir) - 1;
+  dir = buf;
+  while (p > dir && isdirsep (*p))
+    *p-- = '\0';
+ }
       if (!(fh = build_fh_name (dir, PC_SYM_NOFOLLOW)))
  __leave;   /* errno already set */;
 
--
2.21.0

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Re: [PATCH] Cygwin: rmdir: fail if last component is a symlink, as on Linux

Ken Brown-6
On 9/22/2019 1:18 PM, Ken Brown wrote:
[...]

> @@ -354,6 +353,25 @@ rmdir (const char *dir)
>  
>     __try
>       {
> +      if (!*dir)
> + {
> +  set_errno (ENOENT);
> +  __leave;
> + }
> +
> +      /* Following Linux, do not resolve the last component of DIR if
> + it is a symlink, even if DIR has a trailing slash.  Achieve
> + this by stripping trailing slashes or backslashes.  */
> +      if (isdirsep (dir[strlen (dir) - 1]))
> + {
> +  /* This converts // to /, but since both give ENOTEMPTY,
> +     we're okay.  */
> +  char *buf;
> +  char *p = stpcpy (buf = tp.c_get (), dir) - 1;

I forgot to declare tp.  v2 is on the way.

Ken