smb/client: Prevent error pointer dereference

The cifs_sb_tlink() function can return error pointers, but this code
dereferences it before checking for error pointers.  Re-order the code
to fix that.

Fixes: 0f9b6b045bb2 ("fs/smb/client: implement chmod() for SMB3 POSIX Extensions")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Bharath SM <bharathsm@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb/client/cifsacl.c

@@ -1592,14 +1592,16 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode,
 	struct smb_ntsd *pntsd = NULL; /* acl obtained from server */
 	struct smb_ntsd *pnntsd = NULL; /* modified acl to be sent to server */
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
-	struct tcon_link *tlink = cifs_sb_tlink(cifs_sb);
+	struct tcon_link *tlink;
 	struct smb_version_operations *ops;
 	bool mode_from_sid, id_from_sid;
-	bool posix = tlink_tcon(tlink)->posix_extensions;
 	const u32 info = 0;
+	bool posix;
 
+	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink))
 		return PTR_ERR(tlink);
+	posix = tlink_tcon(tlink)->posix_extensions;
 
 	ops = tlink_tcon(tlink)->ses->server->ops;