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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 <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Bart Van Assche 2016-11-18 14:28:00 -08:00 committed by Mike Snitzer
parent b23df0d048
commit 6080758d44
1 changed files with 1 additions and 1 deletions
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2
drivers/md/dm-ioctl.c
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@ -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;