smb3: warn on confusing error scenario with sec=krb5

commit 0a018944eee913962bce8ffebbb121960d5125d9 upstream.

When mounting with Kerberos, users have been confused about the
default error returned in scenarios in which either keyutils is
not installed or the user did not properly acquire a krb5 ticket.
Log a warning message in the case that "ENOKEY" is returned
from the get_spnego_key upcall so that users can better understand
why mount failed in those two cases.

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 1c87a429ce72f66f5d65e70a845ed1a7b03abe9f..2097b5fd51baaa597ab0368d97efcbb08844029e 100644 (file)
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -942,6 +942,8 @@ SMB2_auth_kerberos(struct SMB2_sess_data *sess_data)
        spnego_key = cifs_get_spnego_key(ses);
        if (IS_ERR(spnego_key)) {
                rc = PTR_ERR(spnego_key);
+               if (rc == -ENOKEY)
+                       cifs_dbg(VFS, "Verify user has a krb5 ticket and keyutils is installed\n");
                spnego_key = NULL;
                goto out;
        }