Re: [PATCHv2] mmc: block: ensure error propagation for non-blk

[Adrian Hunter <adrian.hunter@intel.com>]

On 26/04/23 19:59, Christian Loehle wrote:
> 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: 614f0388f580 ("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>

> ---
> v2: Adopted Adrians suggestions to set the error before calling
> 	and rewrote commit message
>  drivers/mmc/core/block.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 672ab90c4b2d..0ff294f07465 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -266,6 +266,7 @@ 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);
> @@ -653,6 +654,7 @@ 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);
> @@ -724,6 +726,7 @@ 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);
> @@ -2808,6 +2811,7 @@ 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) {
> @@ -2846,6 +2850,7 @@ 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;