linux-kernel - Re: [PATCH] mmc: queue: ensure error propagation for non-blk

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Date:   Tue, 25 Apr 2023 17:01:16 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Christian Loehle <CLoehle@...erstone.com>,
        ulf hansson <ulf.hansson@...aro.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Avri Altman <avri.altman@....com>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] mmc: queue: ensure error propagation for non-blk

On 24/04/23 19:22, Christian Loehle wrote:
> Requests to the mmc layer usually come through a block device.
> The exceptions are the RPMB chardev and debugfs, which issue their
> own blk_mq requests through blk_execute_rq and do not query
> the BLK_STS error but the mmc-internal drv_op_result.
> This patch ensures that drv_op_result is set as error whenever
> a BLK_STS error is set.
> 
> The behavior leads to a bug where the request never sees 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 the error 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 completely by always setting
> drv_op_result in case of a BLK_STS error.
> 
> Signed-off-by: Christian Loehle <cloehle@...erstone.com>

Fixes tag?

> ---
>  drivers/mmc/core/queue.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
> index b396e3900717..8240962e28f3 100644
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -334,6 +334,9 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
>  		WRITE_ONCE(mq->busy, false);
>  	}
>  
> +	/* Ensure request error propagates to non-blk callers, too. */
> +	if (!req_to_mmc_queue_req(req)->drv_op_result && ret)
> +		req_to_mmc_queue_req(req)->drv_op_result = ret;

That is not the only path out.

It might be better to initialize drv_op_result to an
error code to start with e.g.

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 00c33edb9fb9..d920c4178389 100644
--- a/drivers/mmc/core/block.c
+++ b/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;


>  	return ret;
>  }
>