Re: [PATCH 3/7] cifs: Add support for creating native Windows sockets

["Pali Rohár" <pali@kernel.org>]

On Sunday 06 October 2024 12:00:42 Pali Rohár wrote:
> Native Windows sockets created by WinSock on Windows 10 April 2018 Update
> (version 1803) or Windows Server 2019 (version 1809) or later versions is
> reparse point with IO_REPARSE_TAG_AF_UNIX tag, with empty reparse point
> data buffer and without any EAs.
> 
> Create AF_UNIX sockets in this native format when -o reparse=native or
> -o reparse=native+<something> mount option is used.
> 
> This change makes AF_UNIX sockets created by Linux CIFS client compatible
> with AF_UNIX sockets created by Windows applications on NTFS volumes.
> 
> Signed-off-by: Pali Rohár <pali@kernel.org>
> ---
>  fs/smb/client/cifsglob.h |  6 +++---
>  fs/smb/client/reparse.c  | 36 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 39 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
> index 7632d2ba5390..570b22d02f7e 100644
> --- a/fs/smb/client/cifsglob.h
> +++ b/fs/smb/client/cifsglob.h
> @@ -155,9 +155,9 @@ enum securityEnum {
>  
>  enum cifs_reparse_type {
>  	CIFS_REPARSE_TYPE_NONE, /* disable creating new reparse points */
> -	CIFS_REPARSE_TYPE_NATIVE, /* native symlinks only */
> -	CIFS_REPARSE_TYPE_NATIVE_NFS, /* native for symlinks, nfs for others */
> -	CIFS_REPARSE_TYPE_NATIVE_WSL, /* native for symlinks, wsl for others */
> +	CIFS_REPARSE_TYPE_NATIVE, /* native symlinks and sockets only, no support for others */
> +	CIFS_REPARSE_TYPE_NATIVE_NFS, /* native for symlinks/sockets, nfs for fifos/block/char */
> +	CIFS_REPARSE_TYPE_NATIVE_WSL, /* native for symlinks/sockets, wsl for fifos/block/char */
>  	CIFS_REPARSE_TYPE_NFS, /* nfs for everything */
>  	CIFS_REPARSE_TYPE_WSL, /* wsl for everything */
>  	CIFS_REPARSE_TYPE_DEFAULT = CIFS_REPARSE_TYPE_NATIVE_NFS,
> diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
> index 38fe0a710c65..f1488f870320 100644
> --- a/fs/smb/client/reparse.c
> +++ b/fs/smb/client/reparse.c
> @@ -379,6 +379,35 @@ static int detect_directory_symlink_target(struct cifs_sb_info *cifs_sb,
>  	return 0;
>  }
>  
> +static int create_native_socket(const unsigned int xid, struct inode *inode,
> +				struct dentry *dentry, struct cifs_tcon *tcon,
> +				const char *full_path)
> +{
> +	struct cifs_open_info_data data = {
> +		.reparse_point = true,
> +		.reparse = { .tag = IO_REPARSE_TAG_AF_UNIX, },
> +	};
> +	struct reparse_data_buffer buf = {
> +		.ReparseTag = cpu_to_le32(IO_REPARSE_TAG_AF_UNIX),
> +		.ReparseDataLength = 0,

Correctly, this should be:

  .ReparseDataLength = cpu_to_le16(0),

> +	};
> +	struct kvec iov = {
> +		.iov_base = &buf,
> +		.iov_len = sizeof(buf),
> +	};
> +	struct inode *new;
> +	int rc;

Here is missing initialization of rc:

  int rc = 0;

> +
> +	new = smb2_get_reparse_inode(&data, inode->i_sb, xid,
> +				     tcon, full_path, false, &iov, NULL);
> +	if (!IS_ERR(new))
> +		d_instantiate(dentry, new);
> +	else
> +		rc = PTR_ERR(new);
> +	cifs_free_open_info(&data);
> +	return rc;
> +}
> +
>  static int nfs_set_reparse_buf(struct reparse_posix_data *buf,
>  			       mode_t mode, dev_t dev,
>  			       struct kvec *iov)
> @@ -602,6 +631,13 @@ int smb2_mknod_reparse(unsigned int xid, struct inode *inode,
>  {
>  	struct smb3_fs_context *ctx = CIFS_SB(inode->i_sb)->ctx;
>  
> +	if (S_ISSOCK(mode) && (
> +	     ctx->reparse_type == CIFS_REPARSE_TYPE_NATIVE ||
> +	     ctx->reparse_type == CIFS_REPARSE_TYPE_NATIVE_NFS ||
> +	     ctx->reparse_type == CIFS_REPARSE_TYPE_NATIVE_WSL)) {
> +		return create_native_socket(xid, inode, dentry, tcon, full_path);
> +	}
> +
>  	switch (ctx->reparse_type) {
>  	case CIFS_REPARSE_TYPE_NATIVE_NFS:
>  	case CIFS_REPARSE_TYPE_NFS:
> -- 
> 2.20.1
>