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 cdad4d933bce064a1f62949284c1387532150d65..cac1eaa2a718396316d4e9b4e00ff922cf8c57fe 100644 (file)
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1347,6 +1347,8 @@ 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;
        }