mmc: block: ensure error propagation for non-blk

Requests to the mmc layer usually come through a block device IO.
The exceptions are the ioctl interface, RPMB chardev ioctl
and debugfs, which issue their own blk_mq requests through
blk_execute_rq and do not query the BLK_STS error but the
mmcblk-internal drv_op_result. This patch ensures that drv_op_result
defaults to an error and has to be overwritten by the operation
to be considered successful.

The behavior leads to a bug where the request never propagates
the error, e.g. by directly erroring out at mmc_blk_mq_issue_rq if
mmc_blk_part_switch fails. The ioctl caller of the rpmb chardev then
can never see an error (BLK_STS_IOERR, but drv_op_result is unchanged)
and thus may assume that their call executed successfully when it did not.

While always checking the blk_execute_rq return value would be
advised, let's eliminate the error by always setting
drv_op_result as -EIO to be overwritten on success (or other error)

Fixes: 614f038 ("mmc: block: move single ioctl() commands to block requests")
Signed-off-by: Christian Loehle <cloehle@hyperstone.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/59c17ada35664b818b7bd83752119b2d@hyperstone.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: cloehle

drivers/mmc/core/block.c

@@ -264,6 +264,7 @@ static ssize_t power_ro_lock_store(struct device *dev,
 		goto out_put;
 	}
 	req_to_mmc_queue_req(req)->drv_op = MMC_DRV_OP_BOOT_WP;
+	req_to_mmc_queue_req(req)->drv_op_result = -EIO;
 	blk_execute_rq(req, false);
 	ret = req_to_mmc_queue_req(req)->drv_op_result;
 	blk_mq_free_request(req);
@@ -651,6 +652,7 @@ static int mmc_blk_ioctl_cmd(struct mmc_blk_data *md,
 	idatas[0] = idata;
 	req_to_mmc_queue_req(req)->drv_op =
 		rpmb ? MMC_DRV_OP_IOCTL_RPMB : MMC_DRV_OP_IOCTL;
+	req_to_mmc_queue_req(req)->drv_op_result = -EIO;
 	req_to_mmc_queue_req(req)->drv_op_data = idatas;
 	req_to_mmc_queue_req(req)->ioc_count = 1;
 	blk_execute_rq(req, false);
@@ -722,6 +724,7 @@ static int mmc_blk_ioctl_multi_cmd(struct mmc_blk_data *md,
 	}
 	req_to_mmc_queue_req(req)->drv_op =
 		rpmb ? MMC_DRV_OP_IOCTL_RPMB : MMC_DRV_OP_IOCTL;
+	req_to_mmc_queue_req(req)->drv_op_result = -EIO;
 	req_to_mmc_queue_req(req)->drv_op_data = idata;
 	req_to_mmc_queue_req(req)->ioc_count = n;
 	blk_execute_rq(req, false);
@@ -2806,6 +2809,7 @@ static int mmc_dbg_card_status_get(void *data, u64 *val)
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 	req_to_mmc_queue_req(req)->drv_op = MMC_DRV_OP_GET_CARD_STATUS;
+	req_to_mmc_queue_req(req)->drv_op_result = -EIO;
 	blk_execute_rq(req, false);
 	ret = req_to_mmc_queue_req(req)->drv_op_result;
 	if (ret >= 0) {
@@ -2844,6 +2848,7 @@ static int mmc_ext_csd_open(struct inode *inode, struct file *filp)
 		goto out_free;
 	}
 	req_to_mmc_queue_req(req)->drv_op = MMC_DRV_OP_GET_EXT_CSD;
+	req_to_mmc_queue_req(req)->drv_op_result = -EIO;
 	req_to_mmc_queue_req(req)->drv_op_data = &ext_csd;
 	blk_execute_rq(req, false);
 	err = req_to_mmc_queue_req(req)->drv_op_result;