On Tue, Apr 5, 2011 at 4:59 PM, John Calixto
<john.calixto@xxxxxxxxxxxxxx> wrote:
> Some ACMDs might actually damage the card. This check ensures the
> caller has CAP_SYS_ADMIN before allowing such an activity.
>
> Signed-off-by: John Calixto <john.calixto@xxxxxxxxxxxxxx>
> ---
> drivers/mmc/card/block.c | 29 +++++++++++++++++++++++++++++
> 1 files changed, 29 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index c2e107c..2ed8c57 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -31,6 +31,7 @@
> #include <linux/mutex.h>
> #include <linux/scatterlist.h>
> #include <linux/string_helpers.h>
> +#include <linux/capability.h>
> #include <linux/compat.h>
> #include <linux/delay.h>
>
> @@ -205,6 +206,34 @@ static int mmc_blk_ioctl_acmd(struct block_device *bdev,
> goto acmd_done;
> }
>
> + /*
> + * The following ACMDs are known to be nondestructive. They are used
> + * by SD security applications (ref: SD Specifications, Part 1,
> + * Physical Layer Simplified Specification, Version 3.01, Table 4-27).
> + * Any other commands require CAP_SYS_ADMIN because they may destroy
> + * the card.
> + */
> + switch (sdic.opcode) {
> + case SD_APP_SD_STATUS:
> + case 18:
> + case 25:
> + case 26:
> + case 38:
> + case 43:
> + case 44:
> + case 45:
> + case 46:
> + case 47:
> + case 48:
> + case 49:
> + break;
> + default:
> + if (!capable(CAP_SYS_ADMIN)) {
> + err = -EPERM;
> + goto acmd_done;
> + }
> + }
> +
> cmd.opcode = sdic.opcode;
> cmd.arg = sdic.arg;
> cmd.flags = sdic.flags;
> --
> 1.7.4.1
Hi John,
Just to clarify, were the commands supposed to exclude commands that do writes?
In MMC-land:
CMD18 is PROGRAM_CID (which is a once-in-a-lifetime operation).
CMD38 is erase
CMD25 is write_multiple_block - this can give a non-root user full
control over a disk, bypassing security.
You should definitely check if the the target device is MMC or SD.
Because the MMC and SD have slightly differing command sets.
A
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