From: Bart Van Assche Date: Fri, 18 Nov 2016 22:28:00 +0000 (-0800) Subject: dm ioctl: use offsetof() instead of open-coding it X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=6080758d441acd7765314f3e9b6ca843e18e9a68;p=linux-beck.git dm ioctl: use offsetof() instead of open-coding it Subtracting sizes is a fragile approach because the result is only correct if the compiler has not added any padding at the end of the structure. Hence use offsetof() instead of size subtraction. An additional advantage of offsetof() is that it makes the intent more clear. Signed-off-by: Bart Van Assche Signed-off-by: Mike Snitzer --- diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 966eb4b61aed..c72a77048b73 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1697,7 +1697,7 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern { struct dm_ioctl *dmi; int secure_data; - const size_t minimum_data_size = sizeof(*param_kernel) - sizeof(param_kernel->data); + const size_t minimum_data_size = offsetof(struct dm_ioctl, data); if (copy_from_user(param_kernel, user, minimum_data_size)) return -EFAULT;