Date:   Tue, 20 Jun 2023 17:48:56 +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: [PATCHv2 2/2] mmc: block: ioctl: Add PROG-error aggregation

On Tue, 20 Jun 2023 at 13:23, 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   | 17 ++++++-----------
> >>  drivers/mmc/core/mmc_ops.c | 25 ++++++++++++++++++++++++-
> >> drivers/mmc/core/mmc_ops.h |  3 +++
> >>  3 files changed, 33 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index
> >> e46330815484..44c1b2825032 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 +604,15 @@ 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 write/R1B execution errors */
> >> +       if (idata->ic.write_flag || r1b_resp)
> >
> > Earlier we polled for requests that were targeted to rpmb, no matter if they were write or reads. Are you intentionally changing this? If so, can you explain why?
> >
> Will re-introduce. I cant really think of a reason right now to do this after rpmb reads, but thats a different story.

Okay, good.

My main point is, if we want to change that, let's do that as a separate patch.

>
> >> +               err = mmc_poll_for_busy_err_flags(card, busy_timeout_ms, false,
> >> +                                       MMC_BUSY_IO,
> >> + &idata->ic.response[0]);
> >
> > I think it's better to extend the mmc_blk_busy_cb, rather than introducing an entirely new polling function.
> >
> > Then you can call __mmc_poll_for_busy() here instead.
>
> Not sure if I understood you right, but I will send a new version with __mmc_poll_for_busy call directly.
> It does feel a bit more awkward, at least to me, because both mmc_blk_busy_cb nor mmc_busy_data are currently only in mmc_ops.c
>
> Anyway, both versions "extend the mmc_blk_busy_cb", so I'm not sure if I understood you correctly, we will see.
> I may also just send both and you pick whichever you prefer.

I was thinking that mmc_blk_card_busy() calls __mmc_poll_for_busy().
While doing that, it uses the mmc_blk_busy_cb() - which seems to be
almost what we want to do here too.

Did that make sense?

Kind regards
Uffe

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