mmc: core: Add mmc CMD+ACMD passthrough ioctl

Allows appropriately-privileged applications to send CMD (normal) and ACMD
(application-specific; preceded with CMD55) commands to cards/devices on
the mmc bus.  This is primarily useful for enabling the security
functionality built in to every SD card.

It can also be used as a generic passthrough (e.g. to enable virtual
machines to control mmc bus devices directly).  However, this use case has
not been tested rigorously.  Generic passthrough testing was only conducted
for a few non-security opcodes to prove the feasibility of the passthrough.

Since any opcode can be sent using this passthrough, it is very possible to
render the card/device unusable.  Applications that use this ioctl must
have CAP_SYS_RAWIO.

Security commands tested on TI PCIxx12 (SDHCI), Sigma Designs SMP8652 SoC,
TI OMAP3621/OMAP3630 SoC, Samsung S5PC110 SoC, Qualcomm MSM7200A SoC.

Signed-off-by: John Calixto <john.calixto@modsystems.com>
Reviewed-by: Andrei Warkentin <andreiw@motorola.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

2 files changed, 203 insertions, 1 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index e7efd6faeaf9..407836d55712 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -31,7 +31,11 @@
 #include <linux/mutex.h>
 #include <linux/scatterlist.h>
 #include <linux/string_helpers.h>
+#include <linux/delay.h>
+#include <linux/capability.h>
+#include <linux/compat.h>
 
+#include <linux/mmc/ioctl.h>
 #include <linux/mmc/card.h>
 #include <linux/mmc/host.h>
 #include <linux/mmc/mmc.h>
@@ -218,11 +222,208 @@ mmc_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
         return 0;
 }
 
+struct mmc_blk_ioc_data {
+        struct mmc_ioc_cmd ic;
+        unsigned char *buf;
+        u64 buf_bytes;
+};
+
+static struct mmc_blk_ioc_data *mmc_blk_ioctl_copy_from_user(
+        struct mmc_ioc_cmd __user *user)
+{
+        struct mmc_blk_ioc_data *idata;
+        int err;
+
+        idata = kzalloc(sizeof(*idata), GFP_KERNEL);
+        if (!idata) {
+                err = -ENOMEM;
+                goto copy_err;
+        }
+
+        if (copy_from_user(&idata->ic, user, sizeof(idata->ic))) {
+                err = -EFAULT;
+                goto copy_err;
+        }
+
+        idata->buf_bytes = (u64) idata->ic.blksz * idata->ic.blocks;
+        if (idata->buf_bytes > MMC_IOC_MAX_BYTES) {
+                err = -EOVERFLOW;
+                goto copy_err;
+        }
+
+        idata->buf = kzalloc(idata->buf_bytes, GFP_KERNEL);
+        if (!idata->buf) {
+                err = -ENOMEM;
+                goto copy_err;
+        }
+
+        if (copy_from_user(idata->buf, (void __user *)(unsigned long)
+                                        idata->ic.data_ptr, idata->buf_bytes)) {
+                err = -EFAULT;
+                goto copy_err;
+        }
+
+        return idata;
+
+copy_err:
+        kfree(idata->buf);
+        kfree(idata);
+        return ERR_PTR(err);
+
+}
+
+static int mmc_blk_ioctl_cmd(struct block_device *bdev,
+        struct mmc_ioc_cmd __user *ic_ptr)
+{
+        struct mmc_blk_ioc_data *idata;
+        struct mmc_blk_data *md;
+        struct mmc_card *card;
+        struct mmc_command cmd = {0};
+        struct mmc_data data = {0};
+        struct mmc_request mrq = {0};
+        struct scatterlist sg;
+        int err;
+
+        /*
+         * The caller must have CAP_SYS_RAWIO, and must be calling this on the
+         * whole block device, not on a partition.  This prevents overspray
+         * between sibling partitions.
+         */
+        if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
+                return -EPERM;
+
+        idata = mmc_blk_ioctl_copy_from_user(ic_ptr);
+        if (IS_ERR(idata))
+                return PTR_ERR(idata);
+
+        cmd.opcode = idata->ic.opcode;
+        cmd.arg = idata->ic.arg;
+        cmd.flags = idata->ic.flags;
+
+        data.sg = &sg;
+        data.sg_len = 1;
+        data.blksz = idata->ic.blksz;
+        data.blocks = idata->ic.blocks;
+
+        sg_init_one(data.sg, idata->buf, idata->buf_bytes);
+
+        if (idata->ic.write_flag)
+                data.flags = MMC_DATA_WRITE;
+        else
+                data.flags = MMC_DATA_READ;
+
+        mrq.cmd = &cmd;
+        mrq.data = &data;
+
+        md = mmc_blk_get(bdev->bd_disk);
+        if (!md) {
+                err = -EINVAL;
+                goto cmd_done;
+        }
+
+        card = md->queue.card;
+        if (IS_ERR(card)) {
+                err = PTR_ERR(card);
+                goto cmd_done;
+        }
+
+        mmc_claim_host(card->host);
+
+        if (idata->ic.is_acmd) {
+                err = mmc_app_cmd(card->host, card);
+                if (err)
+                        goto cmd_rel_host;
+        }
+
+        /* data.flags must already be set before doing this. */
+        mmc_set_data_timeout(&data, card);
+        /* Allow overriding the timeout_ns for empirical tuning. */
+        if (idata->ic.data_timeout_ns)
+                data.timeout_ns = idata->ic.data_timeout_ns;
+
+        if ((cmd.flags & MMC_RSP_R1B) == MMC_RSP_R1B) {
+                /*
+                 * Pretend this is a data transfer and rely on the host driver
+                 * to compute timeout.  When all host drivers support
+                 * cmd.cmd_timeout for R1B, this can be changed to:
+                 *
+                 *     mrq.data = NULL;
+                 *     cmd.cmd_timeout = idata->ic.cmd_timeout_ms;
+                 */
+                data.timeout_ns = idata->ic.cmd_timeout_ms * 1000000;
+        }
+
+        mmc_wait_for_req(card->host, &mrq);
+
+        if (cmd.error) {
+                dev_err(mmc_dev(card->host), "%s: cmd error %d\n",
+                                                __func__, cmd.error);
+                err = cmd.error;
+                goto cmd_rel_host;
+        }
+        if (data.error) {
+                dev_err(mmc_dev(card->host), "%s: data error %d\n",
+                                                __func__, data.error);
+                err = data.error;
+                goto cmd_rel_host;
+        }
+
+        /*
+         * According to the SD specs, some commands require a delay after
+         * issuing the command.
+         */
+        if (idata->ic.postsleep_min_us)
+                usleep_range(idata->ic.postsleep_min_us, idata->ic.postsleep_max_us);
+
+        if (copy_to_user(&(ic_ptr->response), cmd.resp, sizeof(cmd.resp))) {
+                err = -EFAULT;
+                goto cmd_rel_host;
+        }
+
+        if (!idata->ic.write_flag) {
+                if (copy_to_user((void __user *)(unsigned long) idata->ic.data_ptr,
+                                                idata->buf, idata->buf_bytes)) {
+                        err = -EFAULT;
+                        goto cmd_rel_host;
+                }
+        }
+
+cmd_rel_host:
+        mmc_release_host(card->host);
+
+cmd_done:
+        mmc_blk_put(md);
+        kfree(idata->buf);
+        kfree(idata);
+        return err;
+}
+
+static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
+        unsigned int cmd, unsigned long arg)
+{
+        int ret = -EINVAL;
+        if (cmd == MMC_IOC_CMD)
+                ret = mmc_blk_ioctl_cmd(bdev, (struct mmc_ioc_cmd __user *)arg);
+        return ret;
+}
+
+#ifdef CONFIG_COMPAT
+static int mmc_blk_compat_ioctl(struct block_device *bdev, fmode_t mode,
+        unsigned int cmd, unsigned long arg)
+{
+        return mmc_blk_ioctl(bdev, mode, cmd, (unsigned long) compat_ptr(arg));
+}
+#endif
+
 static const struct block_device_operations mmc_bdops = {
         .open                   = mmc_blk_open,
         .release                = mmc_blk_release,
         .getgeo                 = mmc_blk_getgeo,
         .owner                  = THIS_MODULE,
+        .ioctl                  = mmc_blk_ioctl,
+#ifdef CONFIG_COMPAT
+        .compat_ioctl           = mmc_blk_compat_ioctl,
+#endif
 };
 
 struct mmc_blk_request {
diff --git a/drivers/mmc/core/sd_ops.c b/drivers/mmc/core/sd_ops.c
index a206aea5360d..021fed153804 100644
--- a/drivers/mmc/core/sd_ops.c
+++ b/drivers/mmc/core/sd_ops.c
@@ -21,7 +21,7 @@
 #include "core.h"
 #include "sd_ops.h"
 
-static int mmc_app_cmd(struct mmc_host *host, struct mmc_card *card)
+int mmc_app_cmd(struct mmc_host *host, struct mmc_card *card)
 {
         int err;
         struct mmc_command cmd = {0};
@@ -49,6 +49,7 @@ static int mmc_app_cmd(struct mmc_host *host, struct mmc_card *card)
 
         return 0;
 }
+EXPORT_SYMBOL_GPL(mmc_app_cmd);
 
 /**
  *      mmc_wait_for_app_cmd - start an application command and wait for