Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Pascal van Leeuwen <pvanleeuwen@rambus.com>
To:     linux-crypto@vger.kernel.org
Cc:     antoine.tenart@bootlin.com, herbert@gondor.apana.org.au,
        davem@davemloft.net, Pascal van Leeuwen <pvanleeuwen@rambus.com>
Subject: [PATCH] crypto: inside-secure - Prevent missing of processing errors
Date:   Tue,  8 Sep 2020 08:10:45 +0200
Message-Id: <1599545445-5716-1-git-send-email-pvanleeuwen@rambus.com>
Feedback-ID: 580919m:580919aJ_Wy3x:580919sVzW-zOjoc
Sender: linux-crypto-owner@vger.kernel.org
Precedence: bulk

On systems with coherence issues, packet processed could succeed while
it should have failed, e.g. because of an authentication fail.
This is because the driver would read stale status information that had
all error bits initialised to zero = no error.
Since this is potential a security risk, we want to prevent it from being
a possibility at all. So initialize all error bits to error state, so
that reading stale status information will always result in errors.

Signed-off-by: Pascal van Leeuwen <pvanleeuwen@rambus.com>
---
 drivers/crypto/inside-secure/safexcel_ring.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/inside-secure/safexcel_ring.c b/drivers/crypto/inside-secure/safexcel_ring.c
index e454c3d..90f1503 100644
--- a/drivers/crypto/inside-secure/safexcel_ring.c
+++ b/drivers/crypto/inside-secure/safexcel_ring.c
@@ -236,8 +236,8 @@ struct safexcel_result_desc *safexcel_add_rdesc(struct safexcel_crypto_priv *pri
 
 	rdesc->particle_size = len;
 	rdesc->rsvd0 = 0;
-	rdesc->descriptor_overflow = 0;
-	rdesc->buffer_overflow = 0;
+	rdesc->descriptor_overflow = 1; /* assume error */
+	rdesc->buffer_overflow = 1;     /* assume error */
 	rdesc->last_seg = last;
 	rdesc->first_seg = first;
 	rdesc->result_size = EIP197_RD64_RESULT_SIZE;
@@ -245,9 +245,10 @@ struct safexcel_result_desc *safexcel_add_rdesc(struct safexcel_crypto_priv *pri
 	rdesc->data_lo = lower_32_bits(data);
 	rdesc->data_hi = upper_32_bits(data);
 
-	/* Clear length & error code in result token */
+	/* Clear length in result token */
 	rtoken->packet_length = 0;
-	rtoken->error_code = 0;
+	/* Assume errors - HW will clear if not the case */
+	rtoken->error_code = 0x7fff;
 
 	return rdesc;
 }
-- 
1.8.3.1