linux-kernel - Re: [PATCHv3 1/1] mmc: block: ioctl: Add PROG-error aggregation

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Date:   Thu, 22 Jun 2023 11:45:31 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Christian Loehle <CLoehle@...erstone.com>
Cc:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Avri Altman <avri.altman@....com>
Subject: Re: [PATCHv3 1/1] mmc: block: ioctl: Add PROG-error aggregation

On Tue, 20 Jun 2023 at 14:44, Christian Loehle <CLoehle@...erstone.com> wrote:
>
> Userspace currently has no way of checking for error bits of
> detection mode X. These are error bits that are only detected by
> the card when executing the command. For e.g. a sanitize operation
> this may be minutes after the RSP was seen by the host.
>
> Currently userspace programs cannot see these error bits reliably.
> They could issue a multi ioctl cmd with a CMD13 immediately following
> it, but since errors of detection mode X are automatically cleared
> (they are all clear condition B).
> mmc_poll_for_busy of the first ioctl may have already hidden such an
> error flag.
>
> In case of the security operations: sanitize, secure erases and
> RPMB writes, this could lead to the operation not being performed
> successfully by the card with the user not knowing.
> If the user trusts that this operation is completed
> (e.g. their data is sanitized), this could be a security issue.
> An attacker could e.g. provoke a eMMC (VCC) flash fail, where a
> successful sanitize of a card is not possible. A card may move out
> of PROG state but issue a bit 19 R1 error.
>
> This patch therefore will also have the consequence of a mmc-utils
> patch, which enables the bit for the security-sensitive operations.
>
> Signed-off-by: Christian Loehle <cloehle@...erstone.com>
> ---
>  drivers/mmc/core/block.c   | 26 +++++++++++++++-----------
>  drivers/mmc/core/mmc_ops.c | 14 +++++++-------
>  drivers/mmc/core/mmc_ops.h |  9 +++++++++
>  3 files changed, 31 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index e46330815484..c7e2b8ae58a9 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -470,7 +470,7 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
>         struct mmc_data data = {};
>         struct mmc_request mrq = {};
>         struct scatterlist sg;
> -       bool r1b_resp, use_r1b_resp = false;
> +       bool r1b_resp;
>         unsigned int busy_timeout_ms;
>         int err;
>         unsigned int target_part;
> @@ -551,8 +551,7 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
>         busy_timeout_ms = idata->ic.cmd_timeout_ms ? : MMC_BLK_TIMEOUT_MS;
>         r1b_resp = (cmd.flags & MMC_RSP_R1B) == MMC_RSP_R1B;
>         if (r1b_resp)
> -               use_r1b_resp = mmc_prepare_busy_cmd(card->host, &cmd,
> -                                                   busy_timeout_ms);
> +               mmc_prepare_busy_cmd(card->host, &cmd, busy_timeout_ms);
>
>         mmc_wait_for_req(card->host, &mrq);
>         memcpy(&idata->ic.response, cmd.resp, sizeof(cmd.resp));
> @@ -605,19 +604,24 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
>         if (idata->ic.postsleep_min_us)
>                 usleep_range(idata->ic.postsleep_min_us, idata->ic.postsleep_max_us);
>
> -       /* No need to poll when using HW busy detection. */
> -       if ((card->host->caps & MMC_CAP_WAIT_WHILE_BUSY) && use_r1b_resp)
> -               return 0;
> -
>         if (mmc_host_is_spi(card->host)) {
>                 if (idata->ic.write_flag || r1b_resp || cmd.flags & MMC_RSP_SPI_BUSY)
>                         return mmc_spi_err_check(card);
>                 return err;
>         }
> -       /* Ensure RPMB/R1B command has completed by polling with CMD13. */
> -       if (idata->rpmb || r1b_resp)
> -               err = mmc_poll_for_busy(card, busy_timeout_ms, false,
> -                                       MMC_BUSY_IO);
> +       /* Poll for RPMB/write/R1B execution errors */

Except for the other comments that I had on v2 (which isn't addressed
in v3), I would like this comment to be extended a bit.

More precisely, we somehow need to state that even if the host
supports HW busy signaling (MMC_CAP_WAIT_WHILE_BUSY) we need to send a
CMD13 to get the internal error status of the card.

> +       if (idata->rpmb || idata->ic.write_flag || r1b_resp) {
> +               struct mmc_busy_data cb_data;
> +
> +               cb_data.card = card;
> +               cb_data.retry_crc_err = false;
> +               cb_data.aggregate_err_flags = true;
> +               cb_data.busy_cmd = MMC_BUSY_IO;
> +               cb_data.status = &idata->ic.response[0];
> +               err = __mmc_poll_for_busy(card->host, 0, busy_timeout_ms,
> +                               &mmc_busy_cb, &cb_data);
> +
> +       }
>
>         return err;
>  }

[...]

Kind regards
Uffe