[PATCH 3/4] scsi: target: Fix WRITE_SAME NDOB handling in iblock

[Mike Christie <michael.christie@xxxxxxxxxx>]

If NDOB is set we don't have a buffer and we will crash when we access
the t_data_sg. This has us allocate a page to use for the data
buffer that gets passed to the block layer. For the
iblock_execute_zero_out case we just add a check for if NDOB was set.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
 drivers/target/target_core_iblock.c | 36 ++++++++++++++++++++++++-----
 drivers/target/target_core_iblock.h |  1 +
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index 378c80313a0f..767ed2e9474b 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -320,6 +320,9 @@ static void iblock_complete_cmd(struct se_cmd *cmd)
 		status = SAM_STAT_GOOD;
 
 	target_complete_cmd(cmd, status);
+
+	if (ibr->pg)
+		__free_page(ibr->pg);
 	kfree(ibr);
 }
 
@@ -444,13 +447,17 @@ iblock_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
 }
 
 static sense_reason_t
-iblock_execute_zero_out(struct block_device *bdev, struct se_cmd *cmd)
+iblock_execute_zero_out(struct block_device *bdev, struct se_cmd *cmd,
+			bool ndob)
 {
 	struct se_device *dev = cmd->se_dev;
 	struct scatterlist *sg = &cmd->t_data_sg[0];
 	unsigned char *buf, *not_zero;
 	int ret;
 
+	if (ndob)
+		goto issue_zero;
+
 	buf = kmap(sg_page(sg)) + sg->offset;
 	if (!buf)
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
@@ -464,6 +471,7 @@ iblock_execute_zero_out(struct block_device *bdev, struct se_cmd *cmd)
 	if (not_zero)
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 
+issue_zero:
 	ret = blkdev_issue_zeroout(bdev,
 				target_to_linux_sector(dev, cmd->t_task_lba),
 				target_to_linux_sector(dev,
@@ -481,13 +489,15 @@ iblock_execute_write_same(struct se_cmd *cmd)
 {
 	struct block_device *bdev = IBLOCK_DEV(cmd->se_dev)->ibd_bd;
 	struct iblock_req *ibr;
-	struct scatterlist *sg;
+	struct scatterlist *sg, ndob_sg;
+	struct page *pg = NULL;
 	struct bio *bio;
 	struct bio_list list;
 	struct se_device *dev = cmd->se_dev;
 	sector_t block_lba = target_to_linux_sector(dev, cmd->t_task_lba);
 	sector_t sectors = target_to_linux_sector(dev,
 					sbc_get_write_same_sectors(cmd));
+	bool ndob = cmd->t_task_cdb[1] & 0x01;
 
 	if (cmd->prot_op) {
 		pr_err("WRITE_SAME: Protection information with IBLOCK"
@@ -497,7 +507,7 @@ iblock_execute_write_same(struct se_cmd *cmd)
 	sg = &cmd->t_data_sg[0];
 
 	if (cmd->t_data_nents > 1 ||
-	    sg->length != cmd->se_dev->dev_attrib.block_size) {
+	    (sg && sg->length != cmd->se_dev->dev_attrib.block_size)) {
 		pr_err("WRITE_SAME: Illegal SGL t_data_nents: %u length: %u"
 			" block_size: %u\n", cmd->t_data_nents, sg->length,
 			cmd->se_dev->dev_attrib.block_size);
@@ -505,14 +515,26 @@ iblock_execute_write_same(struct se_cmd *cmd)
 	}
 
 	if (bdev_write_zeroes_sectors(bdev)) {
-		if (!iblock_execute_zero_out(bdev, cmd))
+		if (!iblock_execute_zero_out(bdev, cmd, ndob))
 			return 0;
 	}
 
+	if (ndob) {
+		pg = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		if (!pg)
+			return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+
+		sg_init_table(&ndob_sg, 1);
+		sg_set_page(&ndob_sg, pg, cmd->se_dev->dev_attrib.block_size,
+			    0);
+		sg = &ndob_sg;
+	}
+
 	ibr = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);
 	if (!ibr)
-		goto fail;
+		goto fail_free_pg;
 	cmd->priv = ibr;
+	ibr->pg = pg;
 
 	bio = iblock_get_bio(cmd, block_lba, 1, REQ_OP_WRITE);
 	if (!bio)
@@ -548,7 +570,9 @@ iblock_execute_write_same(struct se_cmd *cmd)
 		bio_put(bio);
 fail_free_ibr:
 	kfree(ibr);
-fail:
+fail_free_pg:
+	if (pg)
+		__free_page(pg);
 	return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 }
 
diff --git a/drivers/target/target_core_iblock.h b/drivers/target/target_core_iblock.h
index 8c55375d2f75..0f3cf72b544b 100644
--- a/drivers/target/target_core_iblock.h
+++ b/drivers/target/target_core_iblock.h
@@ -14,6 +14,7 @@
 struct iblock_req {
 	refcount_t pending;
 	atomic_t ib_bio_err_cnt;
+	struct page *pg;
 } ____cacheline_aligned;
 
 #define IBDF_HAS_UDEV_PATH		0x01
-- 
2.25.1