Re: [PATCH] Fix SMB311 posix special file creation to servers which do not advertise reparse support

[Greg KH <gregkh@linuxfoundation.org>]

On Sun, Jul 20, 2025 at 11:32:48PM +0300, Ahmet Eray Karadag wrote:
> From: Steve French <stfrench@microsoft.com>
> 
> Some servers (including Samba), support the SMB3.1.1 POSIX Extensions (which use reparse
> points for handling special files) but do not properly advertise file system attribute
> FILE_SUPPORTS_REPARSE_POINTS.  Although we don't check for this attribute flag when
> querying special file information, we do check it when creating special files which
> causes them to fail unnecessarily.   If we have negotiated SMB3.1.1 POSIX Extensions
> with the server we can expect the server to support creating special files via
> reparse points, and even if the server fails the operation due to really forbidding
> creating special files, then it should be no problem and is more likely to return a
> more accurate rc in any case (e.g. EACCES instead of EOPNOTSUPP).
> 
> Allow creating special files as long as the server supports either reparse points
> or the SMB3.1.1 POSIX Extensions (note that if the "sfu" mount option is specified
> it uses a different way of storing special files that does not rely on reparse points).
> 
> Cc: <stable@vger.kernel.org>
> Fixes: 6c06be908ca19 ("cifs: Check if server supports reparse points before using them")
> Acked-by: Ralph Boehme <slow@samba.org>
> Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
> Signed-off-by: Steve French <stfrench@microsoft.com>
> Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
> ---
>  fs/smb/client/smb2inode.c | 3 ++-
>  fs/smb/client/smb2ops.c   | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
> index 2a3e46b8e15a..a11a2a693c51 100644
> --- a/fs/smb/client/smb2inode.c
> +++ b/fs/smb/client/smb2inode.c
> @@ -1346,7 +1346,8 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
>  	 * empty object on the server.
>  	 */
>  	if (!(le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS))
> -		return ERR_PTR(-EOPNOTSUPP);
> +		if (!tcon->posix_extensions)
> +			return ERR_PTR(-EOPNOTSUPP);
>  
>  	oparms = CIFS_OPARMS(cifs_sb, tcon, full_path,
>  			     SYNCHRONIZE | DELETE |
> diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
> index cb659256d219..938a8a7c5d21 100644
> --- a/fs/smb/client/smb2ops.c
> +++ b/fs/smb/client/smb2ops.c
> @@ -5260,7 +5260,8 @@ static int smb2_make_node(unsigned int xid, struct inode *inode,
>  	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL) {
>  		rc = cifs_sfu_make_node(xid, inode, dentry, tcon,
>  					full_path, mode, dev);
> -	} else if (le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS) {
> +	} else if ((le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS)
> +		|| (tcon->posix_extensions)) {
>  		rc = smb2_mknod_reparse(xid, inode, dentry, tcon,
>  					full_path, mode, dev);
>  	}
> -- 
> 2.34.1
> 
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>