ufs: rpmb: make RPMB usable with OP-TEE key derivation

ufs: rpmb: make RPMB usable with OP-TEE key derivation

[Jorge Ramirez-Ortiz]

This series makes UFS RPMB work out of the box with an OP-TEE that
implements the standard eMMC RPMB key-derivation flow, without requiring
any fundamental changes on the OP-TEE side.

RPMB provides an authenticated, replay-protected storage area whose
security relies on a secret authentication key. In our setup that key is
never exposed to the kernel: OP-TEE derives it in the secure world from
its hardware-unique key and a device identifier (dev_id) that the RPMB
core hands down. OP-TEE's implementation targets eMMC, where dev_id is
the 16-byte eMMC CID, and both the fixed length and the raw-CID layout
are baked into its key derivation.

Two things stand in the way of reusing that same, unmodified OP-TEE flow
for UFS RPMB:

  1. On a cold boot the very first frame sent to the RPMB well-known LU
     comes back with a power-on UNIT ATTENTION (ASC 0x29), which the SCSI
     core reports rather than retries. RPMB has no earlier guaranteed
     access that could clear the condition first, so RPMB fails on every
     power cycle. Patch 1 asks the SCSI core to retry the power-on UNIT
     ATTENTION on the RPMB WLUN.

  2. The UFS RPMB id is "<device_id>-R<region>", which is variable length
     and longer than 16 bytes. Passing it verbatim would tie the derived
     key to a length OP-TEE does not expect and diverge from the fixed
     eMMC CID ABI. Patch 2 hashes it into a fixed 16-byte dev_id with
     blake2s, keeping the key stable and unique per region while matching
     the eMMC CID layout OP-TEE relies on. The hash algorithm and input
     string are thus part of the key-derivation ABI and must stay stable.

With both patches, UFS RPMB is functional from the first access after a
cold boot and derives keys through the existing eMMC-style OP-TEE flow,
(requires minimal OP-TEE changes).

Jorge Ramirez-Ortiz (2):
  ufs: rpmb: retry power-on UNIT ATTENTION on the RPMB WLUN
  ufs: rpmb: use a fixed-length RPMB dev_id

 drivers/ufs/Kconfig         |  1 +
 drivers/ufs/core/ufs-rpmb.c | 41 ++++++++++++++++++++++++++++++++++---
 2 files changed, 39 insertions(+), 3 deletions(-)

[PATCH 1/2] ufs: rpmb: retry power-on UNIT ATTENTION on the RPMB WLUN

[Jorge Ramirez-Ortiz]

After a power cycle, the first command sent to a UFS logical unit
completes with CHECK CONDITION and a power-on UNIT ATTENTION (ASC
0x29). The SCSI core reports this to the caller instead of retrying
it. For the RPMB well-known LU, that first command is the first RPMB
frame sent after boot, so the frame fails. RPMB has no earlier,
guaranteed access that could clear the condition beforehand, so this
breaks RPMB on every cold boot.

Ask the SCSI core to retry the power-on UNIT ATTENTION on the RPMB WLUN
so that RPMB works from the very first access after a power cycle.

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez@oss.qualcomm.com>
---
 drivers/ufs/core/ufs-rpmb.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/ufs/core/ufs-rpmb.c b/drivers/ufs/core/ufs-rpmb.c
index ffad049872b9..adbec80cf381 100644
--- a/drivers/ufs/core/ufs-rpmb.c
+++ b/drivers/ufs/core/ufs-rpmb.c
@@ -40,6 +40,25 @@ struct ufs_rpmb_dev {
 static int ufs_sec_submit(struct ufs_hba *hba, u16 spsp, void *buffer, size_t len, bool send)
 {
 	struct scsi_device *sdev = hba->ufs_rpmb_wlun;
+	struct scsi_sense_hdr sshdr;
+	/* Retry the power-on UNIT ATTENTION (ASC 0x29); the SCSI core does not. */
+	struct scsi_failure failure_defs[] = {
+		{
+			.sense = UNIT_ATTENTION,
+			.asc = SCMD_FAILURE_ASC_ANY,
+			.ascq = SCMD_FAILURE_ASCQ_ANY,
+			.allowed = 3,
+			.result = SAM_STAT_CHECK_CONDITION,
+		},
+		{}
+	};
+	struct scsi_failures failures = {
+		.failure_definitions = failure_defs,
+	};
+	const struct scsi_exec_args exec_args = {
+		.sshdr = &sshdr,
+		.failures = &failures,
+	};
 	u8 cdb[12] = { };
 
 	cdb[0] = send ? SECURITY_PROTOCOL_OUT : SECURITY_PROTOCOL_IN;
@@ -48,7 +67,8 @@ static int ufs_sec_submit(struct ufs_hba *hba, u16 spsp, void *buffer, size_t le
 	put_unaligned_be32(len, &cdb[6]);
 
 	return scsi_execute_cmd(sdev, cdb, send ? REQ_OP_DRV_OUT : REQ_OP_DRV_IN,
-				buffer, len, /*timeout=*/30 * HZ, 0, NULL);
+				buffer, len, /*timeout=*/30 * HZ, /*retries=*/0,
+				&exec_args);
 }
 
 /* UFS RPMB route frames implementation */
-- 
2.54.0

[PATCH 2/2] ufs: rpmb: use a fixed-length RPMB dev_id

[Jorge Ramirez-Ortiz]

The RPMB authentication key is derived from the dev_id handed to the
RPMB subsystem. OP-TEE implements the eMMC RPMB flow, where the dev_id
is the eMMC CID, a fixed 16-byte value, and it derives the key on that
assumption.

The UFS RPMB id built here is "<device_id>-R<region>", which is variable
length and longer than 16 bytes. Passing it verbatim would tie the
derived key to a length OP-TEE does not expect and diverge from the
fixed-CID eMMC ABI, requiring OP-TEE to be taught about variable-length
UFS ids.

Hash the UFS id into a fixed 16-byte dev_id with blake2s instead. This
keeps the derived key stable and unique per region while matching the
eMMC CID layout OP-TEE relies on, so the key-derivation ABI stays
identical and no OP-TEE change is needed.

Select CRYPTO_LIB_BLAKE2S when RPMB is enabled since ufs-rpmb.c now
depends on it.

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez@oss.qualcomm.com>
---
 drivers/ufs/Kconfig         |  1 +
 drivers/ufs/core/ufs-rpmb.c | 19 +++++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/Kconfig b/drivers/ufs/Kconfig
index f662e7ce71f1..0a050565872d 100644
--- a/drivers/ufs/Kconfig
+++ b/drivers/ufs/Kconfig
@@ -7,6 +7,7 @@ menuconfig SCSI_UFSHCD
 	tristate "Universal Flash Storage Controller"
 	depends on SCSI && SCSI_DMA
 	depends on RPMB || !RPMB
+	select CRYPTO_LIB_BLAKE2S if RPMB
 	select PM_DEVFREQ
 	select DEVFREQ_GOV_SIMPLE_ONDEMAND
 	select NLS
diff --git a/drivers/ufs/core/ufs-rpmb.c b/drivers/ufs/core/ufs-rpmb.c
index adbec80cf381..a7595be0884c 100644
--- a/drivers/ufs/core/ufs-rpmb.c
+++ b/drivers/ufs/core/ufs-rpmb.c
@@ -10,6 +10,7 @@
  *	Can Guo <can.guo@oss.qualcomm.com>
  */
 
+#include <crypto/blake2s.h>
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
@@ -21,6 +22,7 @@
 #include <linux/unaligned.h>
 #include "ufshcd-priv.h"
 
+#define UFS_RPMB_ID_LEN			16	/* Match eMMC CID Length */
 #define UFS_RPMB_SEC_PROTOCOL		0xEC	/* JEDEC UFS application */
 #define UFS_RPMB_SEC_PROTOCOL_ID	0x01	/* JEDEC UFS RPMB protocol ID, CDB byte3 */
 
@@ -156,6 +158,7 @@ int ufs_rpmb_probe(struct ufs_hba *hba)
 {
 	struct ufs_rpmb_dev *ufs_rpmb, *it, *tmp;
 	struct rpmb_dev *rdev;
+	char *dev_id = NULL;
 	char *cid = NULL;
 	int region;
 	u32 cap;
@@ -215,8 +218,17 @@ int ufs_rpmb_probe(struct ufs_hba *hba)
 			goto err_out;
 		}
 
-		descr.dev_id = cid;
-		descr.dev_id_len = strlen(cid);
+		dev_id = kzalloc(UFS_RPMB_ID_LEN, GFP_KERNEL);
+		if (!dev_id) {
+			device_unregister(&ufs_rpmb->dev);
+			ret = -ENOMEM;
+			goto err_out;
+		}
+
+		blake2s(NULL, 0, cid, strlen(cid), dev_id, UFS_RPMB_ID_LEN);
+
+		descr.dev_id = dev_id;
+		descr.dev_id_len = UFS_RPMB_ID_LEN;
 		descr.capacity = cap;
 
 		/* Register RPMB device */
@@ -230,6 +242,8 @@ int ufs_rpmb_probe(struct ufs_hba *hba)
 
 		kfree(cid);
 		cid = NULL;
+		kfree(dev_id);
+		dev_id = NULL;
 
 		ufs_rpmb->rdev = rdev;
 		ufs_rpmb->region_id = region;
@@ -242,6 +256,7 @@ int ufs_rpmb_probe(struct ufs_hba *hba)
 	return 0;
 err_out:
 	kfree(cid);
+	kfree(dev_id);
 	list_for_each_entry_safe(it, tmp, &hba->rpmbs, node) {
 		list_del(&it->node);
 		device_unregister(&it->dev);
-- 
2.54.0

Re: [PATCH 1/2] ufs: rpmb: retry power-on UNIT ATTENTION on the RPMB WLUN

[Bart Van Assche]

On 7/15/26 2:39 PM, Jorge Ramirez-Ortiz wrote:
> +	/* Retry the power-on UNIT ATTENTION (ASC 0x29); the SCSI core does not. */

If this patch is reposted please leave out "; the SCSI core does not"
because most developers consider scsi_execute_cmd() as a SCSI core
function. Hence, this patch makes the SCSI core retry upon a power-on
unit attention. Otherwise this patch looks good to me.

Thanks,

Bart.