linux-kernel - Re: [PATCH v3] mmc: core: Return correct emmc response in case of ioctl error

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Message-ID: <CAPDyKFoaXdNDvO91n3rUsqe2JMg5E7YObYDnkAW4jqzVV+GLtw@mail.gmail.com>
Date:   Tue, 24 Aug 2021 14:44:42 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Nishad Kamdar <nishadkamdar@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bean Huo <beanhuo@...ron.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Avri Altman <avri.altman@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mmc: core: Return correct emmc response in case of
 ioctl error

On Thu, 12 Aug 2021 at 08:57, Nishad Kamdar <nishadkamdar@...il.com> wrote:
>
> When a read/write command is sent via ioctl to the kernel,
> and the command fails, the actual error response of the emmc
> is not sent to the user.
>
> IOCTL read/write tests are carried out using commands
> 17 (Single BLock Read), 24 (Single Block Write),
> 18 (Multi Block Read), 25 (Multi Block Write)
>
> The tests are carried out on a 64Gb emmc device. All of these
> tests try to access an "out of range" sector address (0x09B2FFFF).
>
> It is seen that without the patch the response received by the user
> is not OUT_OF_RANGE error (R1 response 31st bit is not set) as per
> JEDEC specification. After applying the patch proper response is seen.
> This is because the function returns without copying the response to
> the user in case of failure. This patch fixes the issue.
>
> The test code and the output of only the CMD17 is included in the
> commit to limit the message length.
>
> CMD17 (Test Code Snippet):
> ==========================
>         printf("Forming CMD%d\n", opt_idx);
>         /*  single block read */
>         cmd.blksz = 512;
>         cmd.blocks = 1;
>         cmd.write_flag = 0;
>         cmd.opcode = 17;
>         //cmd.arg = atoi(argv[3]);
>         cmd.arg = 0x09B2FFFF;
>         /* Expecting response R1B */
>         cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
>
>         memset(data, 0, sizeof(__u8) * 512);
>         mmc_ioc_cmd_set_data(cmd, data);
>
>         printf("Sending CMD%d: ARG[0x%08x]\n", opt_idx, cmd.arg);
>         if(ioctl(fd, MMC_IOC_CMD, &cmd))
>                 perror("Error");
>
>         printf("\nResponse: %08x\n", cmd.response[0]);
>
> CMD17 (Output without patch):
> =============================
> test@...t-LIVA-Z:~$ sudo ./mmc cmd_test /dev/mmcblk0 17
> Entering the do_mmc_commands:Device: /dev/mmcblk0 nargs:4
> Entering the do_mmc_commands:Device: /dev/mmcblk0 options[17, 0x09B2FFF]
> Forming CMD17
> Sending CMD17: ARG[0x09b2ffff]
> Error: Connection timed out
>
> Response: 00000000
> (Incorrect response)
>
> CMD17 (Output with patch):
> ==========================
> test@...t-LIVA-Z:~$ sudo ./mmc cmd_test /dev/mmcblk0 17
> [sudo] password for test:
> Entering the do_mmc_commands:Device: /dev/mmcblk0 nargs:4
> Entering the do_mmc_commands:Device: /dev/mmcblk0 options[17, 09B2FFFF]
> Forming CMD17
> Sending CMD17: ARG[0x09b2ffff]
> Error: Connection timed out
>
> Response: 80000900
> (Correct OUT_OF_ERROR response as per JEDEC specification)
>
> Signed-off-by: Nishad Kamdar <nishadkamdar@...il.com>
> Reviewed-by: Avri Altman <avri.altman@....com>
> ---
> Changes in v2:
>   - Make commit message clearer by adding test cases as outputs.
> Changes in v3:
>   - Shorten the commit message to include only CMD17 related
>     code and test.
>
>  drivers/mmc/core/block.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index a9ad9f5fa9491..efa92aa7e2368 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -522,11 +522,13 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
>         if (cmd.error) {
>                 dev_err(mmc_dev(card->host), "%s: cmd error %d\n",
>                                                 __func__, cmd.error);
> +               memcpy(&idata->ic.response, cmd.resp, sizeof(cmd.resp));
>                 return cmd.error;
>         }
>         if (data.error) {
>                 dev_err(mmc_dev(card->host), "%s: data error %d\n",
>                                                 __func__, data.error);
> +               memcpy(&idata->ic.response, cmd.resp, sizeof(cmd.resp));

It looks like we should do this memcpy, no matter whether we get an
error response or not.

In other words, I suggest you move the existing
"memcpy(&(idata->ic.response), cmd.resp, sizeof(cmd.resp));" from a
couple of lines further done in the code, up to immediately after we
have called mmc_wait_for_req(). That should make it more clear as
well, I think.

>                 return data.error;
>         }
>
> --
> 2.17.1
>

Kind regards
Uffe