Re: [PATCH for-next 1/2] RDMA/qedr: Notify user application if DPM is supported

Leon Romanovsky
2017-06-20T10:41:04Z

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On Tue, Jun 20, 2017 at 08:34:24AM +0000, Amrani, Ram wrote:
> > Um, how is uapi compatibility achieved here? I don't see any size
> > tests related to qedr_alloc_ucontext_resp:
> >
> > struct ib_ucontext *qedr_alloc_ucontext(struct ib_device *ibdev,
> > struct ib_udata *udata)
> > {
> > struct qedr_alloc_ucontext_resp uresp;
> > rc = ib_copy_to_udata(udata, &uresp, sizeof(uresp));
> >
> > Seems bad.
> >
> > Same with the other patch.
> >
> > Jason
>
> It does seem bad. Did you had in mind something like this:
> struct qedr_alloc_ucontext_resp uresp;
> size_t copy_size = min_t(size_t, sizeof(uresp), udata->outlen);
>
> rc = ib_copy_to_udata(udata, &uresp, copy_size);
>
> If so, it makes sense to me to protect everybody's transactions.
> I.e.:
> static inline int ib_copy_to_udata(struct ib_udata *udata, void *src, size_t len)
> {
> size_t copy_size = min_t(size_t, sizeof(uresp), udata->outlen);
> return copy_to_user(udata->outbuf, src, copy_size) ? -EFAULT : 0;
> }
>
> Likewise, a protection can be added for ib_copy_from_udata() too.

mlx4 and mlx5 don't need such protection, because they calculates the
response length and ensure that no extra data is copied.

Thanks

>
> Let me know if I'm missing something. If not, I'll send a patch.
>
> Thanks,
> Ram
>
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