Did anyone find the time to look at this yet?
Any comments?
-----Original Message-----
From: Christian Löhle
Sent: Wednesday, April 5, 2023 1:58 PM
To: Ulf Hansson <ulf.hansson@xxxxxxxxxx>; Adrian Hunter <adrian.hunter@xxxxxxxxx>; linux-mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Cc: Avri Altman <avri.altman@xxxxxxx>
Subject: [PATCH 3/3] mmc: block: ioctl: Add error aggregation flag
> 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@xxxxxxxxxxxxxx>
> ---
> drivers/mmc/core/block.c | 34 ++++++++++++++++++++++++++++++++--
> include/uapi/linux/mmc/ioctl.h | 2 ++
> 2 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index 35ff7101cbb1..386a508bd720 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -457,7 +457,7 @@ static int mmc_blk_ioctl_copy_to_user(struct mmc_ioc_cmd __user *ic_ptr,
> sizeof(ic->response)))
> return -EFAULT;
>
> - if (!idata->ic.write_flag) {
> + if (!idata->ic.write_flag && idata->buf) {
> if (copy_to_user((void __user *)(unsigned long)ic->data_ptr,
> idata->buf, idata->buf_bytes))
> return -EFAULT;
> @@ -610,13 +610,43 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
> 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)
> + if ((card->host->caps & MMC_CAP_WAIT_WHILE_BUSY) && use_r1b_resp &&
> + !(idata->ic.write_flag & MMC_AGGREGATE_PROG_ERRORS))
> return 0;
>
> if (mmc_host_is_spi(card->host)) {
> if (idata->ic.write_flag)
> err = mmc_spi_err_check(card);
> }
> + /*
> + * We want to receive a meaningful R1 response for errors of detection
> + * type X, which are only set after the card has executed the command.
> + * In that case poll CMD13 until PROG is left and return the
> + * accumulated error bits.
> + * If we're lucky host controller has busy detection for R1B and
> + * this is just a single CMD13.
> + * We can abuse resp[1] as the post-PROG R1 here, as all commands
> + * that go through PRG have an R1 response and therefore only
> + * use resp[0].
> + */
> + else if (idata->ic.write_flag & MMC_AGGREGATE_PROG_ERRORS) {
> + unsigned long timeout = jiffies +
> + msecs_to_jiffies(busy_timeout_ms);
> + bool done = false;
> + unsigned long delay_ms = 1;
> + u32 status;
> +
> + do {
> + done = time_after(jiffies, timeout);
> + msleep(delay_ms++);
> + err = __mmc_send_status(card, &status, 1);
> + if (err)
> + return err;
> + idata->ic.response[1] |= status;
> + } while (R1_CURRENT_STATE(status) != R1_STATE_TRAN && !done);
> + if (done)
> + return -ETIMEDOUT;
> + }
> /* Ensure RPMB/R1B command has completed by polling with CMD13. */
> else if (idata->rpmb || r1b_resp)
> err = mmc_poll_for_busy(card, busy_timeout_ms, false, diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h index b2ff7f5be87b..a9d84ae8d57d 100644
> --- a/include/uapi/linux/mmc/ioctl.h
> +++ b/include/uapi/linux/mmc/ioctl.h
> @@ -8,9 +8,11 @@
> struct mmc_ioc_cmd {
> /*
> * Direction of data: nonzero = write, zero = read.
> + * Bit 30 selects error aggregation post-PROG state.
> * Bit 31 selects 'Reliable Write' for RPMB.
> */
> int write_flag;
> +#define MMC_AGGREGATE_PROG_ERRORS (1 << 30)
> #define MMC_RPMB_RELIABLE_WRITE (1 << 31)
>
> /* Application-specific command. true = precede with CMD55 */
> --
> 2.37.3
>
>
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