[PATCH 1/1] scsi: core: Fix error handler encryption support

[Po-Wen Kao <powenkao@google.com>]

From: Brian Kao <powenkao@google.com>

Some low-level drivers (LLD) access block layer crypto fields, such as
rq->crypt_keyslot and rq->crypt_ctx within `struct request`, to
configure hardware for inline encryption.
However, SCSI Error Handling (EH) commands (e.g., TEST UNIT READY,
START STOP UNIT) should not involve any encryption setup.

To prevent drivers from erroneously applying crypto settings during EH,
this patch saves the original values of rq->crypt_keyslot and
rq->crypt_ctx before an EH command is prepared via scsi_eh_prep_cmnd().
These fields in the `struct request` are then set to NULL.
The original values are restored in scsi_eh_restore_cmnd() after the EH
command completes.

This ensures that the block layer crypto context does not leak into
EH command execution.

Tested-by: Brian Kao <powenkao@google.com>
Signed-off-by: Brian Kao <powenkao@google.com>
---
 drivers/scsi/scsi_error.c | 16 ++++++++++++++++
 include/scsi/scsi_eh.h    |  4 ++++
 2 files changed, 20 insertions(+)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 10154d78e3360..2d0df74df703a 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1040,6 +1040,7 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
 			unsigned char *cmnd, int cmnd_size, unsigned sense_bytes)
 {
 	struct scsi_device *sdev = scmd->device;
+	struct request *rq = scsi_cmd_to_rq(scmd);
 
 	/*
 	 * We need saved copies of a number of fields - this is because
@@ -1091,6 +1092,16 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
 		scmd->cmnd[1] = (scmd->cmnd[1] & 0x1f) |
 			(sdev->lun << 5 & 0xe0);
 
+	/*
+	 * Encryption must be disabled for the commands submitted by the error handler.
+	 * Hence, clear the encryption context information.
+	 */
+	ses->rq_crypt_keyslot = rq->crypt_keyslot;
+	ses->rq_crypt_ctx = rq->crypt_ctx;
+
+	rq->crypt_keyslot = NULL;
+	rq->crypt_ctx = NULL;
+
 	/*
 	 * Zero the sense buffer.  The scsi spec mandates that any
 	 * untransferred sense data should be interpreted as being zero.
@@ -1108,6 +1119,8 @@ EXPORT_SYMBOL(scsi_eh_prep_cmnd);
  */
 void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd, struct scsi_eh_save *ses)
 {
+	struct request *rq = scsi_cmd_to_rq(scmd);
+
 	/*
 	 * Restore original data
 	 */
@@ -1120,6 +1133,9 @@ void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd, struct scsi_eh_save *ses)
 	scmd->underflow = ses->underflow;
 	scmd->prot_op = ses->prot_op;
 	scmd->eh_eflags = ses->eh_eflags;
+
+	rq->crypt_keyslot = ses->rq_crypt_keyslot;
+	rq->crypt_ctx = ses->rq_crypt_ctx;
 }
 EXPORT_SYMBOL(scsi_eh_restore_cmnd);
 
diff --git a/include/scsi/scsi_eh.h b/include/scsi/scsi_eh.h
index 1ae08e81339fa..9ef97f7820886 100644
--- a/include/scsi/scsi_eh.h
+++ b/include/scsi/scsi_eh.h
@@ -41,6 +41,10 @@ struct scsi_eh_save {
 	unsigned char cmnd[32];
 	struct scsi_data_buffer sdb;
 	struct scatterlist sense_sgl;
+
+	/* struct request fields */
+	struct bio_crypt_ctx *rq_crypt_ctx;
+	struct blk_crypto_keyslot *rq_crypt_keyslot;
 };
 
 extern void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd,
-- 
2.52.0.177.g9f829587af-goog