Re: [PATCH] mmc: core: check for zero length ioctl data

[Chris Ball <cjb@laptop.org>]

Hi Johan,

On Wed, Nov 23 2011, Johan Rudholm wrote:
> If the read or write buffer size associated with the command sent
> through the mmc_blk_ioctl is zero, do not prepare data buffer.
>
> This enables a ioctl(2) call to for instance send a MMC_SWITCH to set
> a byte in the ext_csd.
>
> Change-Id: Ieab8400ace1ba91bfb3d911377de557bf2d593d0

(Please don't send these tags; I've stripped this one out.)

> Signed-off-by: Johan Rudholm <johan.rudholm@stericsson.com>
> ---
>  drivers/mmc/card/block.c |   82 +++++++++++++++++++++++++---------------------
>  1 files changed, 45 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 12096cc..4d29b30 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -336,6 +336,9 @@ static struct mmc_blk_ioc_data *mmc_blk_ioctl_copy_from_user(
>  		goto idata_err;
>  	}
>  
> +	if (!idata->buf_bytes)
> +		return idata;
> +
>  	idata->buf = kzalloc(idata->buf_bytes, GFP_KERNEL);
>  	if (!idata->buf) {
>  		err = -ENOMEM;
> @@ -382,25 +385,6 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>  	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;
> @@ -413,6 +397,48 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>  		goto cmd_done;
>  	}
>  
> +	cmd.opcode = idata->ic.opcode;
> +	cmd.arg = idata->ic.arg;
> +	cmd.flags = idata->ic.flags;
> +
> +	if (idata->buf_bytes) {
> +		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;
> +
> +		/* 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;
> +		}
> +
> +		mrq.data = &data;
> +	}
> +
> +	mrq.cmd = &cmd;
> +
>  	mmc_claim_host(card->host);
>  
>  	if (idata->ic.is_acmd) {
> @@ -421,24 +447,6 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>  			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) {

Thanks, looks good to me, pushed to mmc-next for 3.3.

Would you be able to share the userspace code that you've been using
with this, please?  I'd like to start collecting a repository of
userspace code showing common uses of this ioctl.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child