Re: [PATCH 1/2] mmc-block: Use memdup_user() rather than duplicating its implementation

walter harms
2016-08-20T09:25:23Z

Am 19.08.2016 23:10, schrieb SF Markus Elfring:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Fri, 19 Aug 2016 22:46:38 +0200
>
> * Reuse existing functionality from memdup_user() instead of keeping
> duplicate source code.
>
> This issue was detected by using the Coccinelle software.
>
> * Delete the integer variable "err" then because the pointer
> variable "idata" should be sufficient to handle return values alone
> in this function.
>
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> drivers/mmc/card/block.c | 26 +++++++++-----------------
> 1 file changed, 9 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 48a5dd7..6ce9492 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -337,22 +337,21 @@ 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 = kmalloc(sizeof(*idata), GFP_KERNEL);
> if (!idata) {
> - err = -ENOMEM;
> + idata = ERR_PTR(-ENOMEM);
> goto out;
> }
>
> if (copy_from_user(&idata->ic, user, sizeof(idata->ic))) {
> - err = -EFAULT;
> + idata = ERR_PTR(-EFAULT);
> goto idata_err;
> }
>
> idata->buf_bytes = (u64) idata->ic.blksz * idata->ic.blocks;
> if (idata->buf_bytes > MMC_IOC_MAX_BYTES) {
> - err = -EOVERFLOW;
> + idata = ERR_PTR(-EOVERFLOW);
> goto idata_err;
> }
>
> @@ -361,26 +360,19 @@ static struct mmc_blk_ioc_data *mmc_blk_ioctl_copy_from_user(
> return idata;
> }
>
> - idata->buf = kmalloc(idata->buf_bytes, GFP_KERNEL);
> - if (!idata->buf) {
> - err = -ENOMEM;
> + idata->buf = memdup_user((void __user *)(unsigned long)
> + idata->ic.data_ptr,
> + idata->buf_bytes);
> + if (IS_ERR(idata->buf)) {
> + idata = (void *) idata->buf;
> goto idata_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);
> idata_err:
> kfree(idata);
> out:
> - return ERR_PTR(err);
> + return idata;
> }

This looks strange, returning a freed pointer is a bad idea. I suggest a
idata=NULL after kfree().

re,
wh

>
> static int mmc_blk_ioctl_copy_to_user(struct mmc_ioc_cmd __user *ic_ptr,