[PATCH v2] Cygwin: rmdir: fail if last component is a symlink, as on Linux

[Eric Blake]

On 9/24/19 12:55 PM, Ken Brown wrote:
> 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 | 27 +++++++++++++++++++++++----
>  1 file changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/winsup/cygwin/dir.cc b/winsup/cygwin/dir.cc
> index b757851d5..0e0535891 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.  */

Maybe even "Following Linux, and intentionally ignoring POSIX, do not..."

> +
> +      /* 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 */;
>  

Looks okay to me.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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