[PATCH v2] Cygwin: path: Add fallback for DFS mounted drive.

[Corinna Vinschen]

Hi Takashi,

On Mar 14 19:57, Takashi Yano wrote:
> - If UNC path for DFS is mounted to a drive with drive letter, the
>   error "Too many levels of symbolic links" occurs when accessing
>   to that drive. This is because GetDosDeviceW() returns unexpected
>   string such as "\Device\Mup\DfsClient\;Z:000000000003fb89\dfsserver
>   \dfs\linkname" for the mounted UNC path "\??\UNC\fileserver\share".
>   This patch adds a workaround for this issue.
> 
>   Addresses: https://cygwin.com/pipermail/cygwin/2022-March/250979.html
> ---
>  winsup/cygwin/path.cc | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
> index 4ad4e0821..dd8f6c043 100644
> --- a/winsup/cygwin/path.cc
> +++ b/winsup/cygwin/path.cc
> @@ -3527,7 +3527,7 @@ restart:
>  		      int remlen = QueryDosDeviceW (drive, remote, MAX_PATH);
>  		      if (remlen < 3)
>  			goto file_not_symlink; /* fallback */
> -		      remlen -= 2;
> +		      remlen -= 2; /* Two L'\0' */
>  
>  		      if (remote[remlen - 1] == L'\\')
>  			remlen--;
> @@ -3535,20 +3535,27 @@ restart:
>  		      UNICODE_STRING rpath;
>  		      RtlInitCountedUnicodeString (&rpath, remote,
>  						   remlen * sizeof (WCHAR));
> +		      const int uncp_len =

I'd still prefer an unsigned type as USHORT or size_t here.  USHORT
because that's the type of the UNICODE_STRING::Length member, or
size_t because that's the standard type used for string lengths.

With that, GTG.

I just notice that remlen is int, too.  Given it represents the return
value from QueryDosDeviceW, it should ideally be converted to DWORD.


Thanks,
Corinna