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SubjectRe: [PATCH v9 12/12] docs: Sample driver to demonstrate how to use Mediated device framework.
On Tue, 18 Oct 2016 10:54:11 +0800
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> * Kirti Wankhede <kwankhede@nvidia.com> [2016-10-18 02:52:12 +0530]:
>
> ...snip...
>
> > +static ssize_t mdev_access(struct mdev_device *mdev, char *buf,
> > + size_t count, loff_t pos, bool is_write)
> > +{
> > + struct mdev_state *mdev_state;
> > + unsigned int index;
> > + loff_t offset;
> > + int ret = 0;
> > +
> > + if (!mdev || !buf)
> > + return -EINVAL;
> > +
> > + mdev_state = mdev_get_drvdata(mdev);
> > + if (!mdev_state) {
> > + pr_err("%s mdev_state not found\n", __func__);
> > + return -EINVAL;
> > + }
> > +
> > + mutex_lock(&mdev_state->ops_lock);
> > +
> > + index = MTTY_VFIO_PCI_OFFSET_TO_INDEX(pos);
> > + offset = pos & MTTY_VFIO_PCI_OFFSET_MASK;
> > + switch (index) {
> > + case VFIO_PCI_CONFIG_REGION_INDEX:
> > +
> > +#if defined(DEBUG)
> > + pr_info("%s: PCI config space %s at offset 0x%llx\n",
> > + __func__, is_write ? "write" : "read", offset);
> > +#endif
> > + if (is_write) {
> > + dump_buffer(buf, count);
> > + handle_pci_cfg_write(mdev_state, offset, buf, count);
> > + } else {
> > + memcpy(buf, (mdev_state->vconfig + offset), count);
> > + dump_buffer(buf, count);
> Dear Kirti:
>
> Shouldn't we use copy_from_user instead of memcpy on @buf here? And I'm
> wondering if dump_buffer could really work since it tries to dereference
> a *__user* marked pointor.

I agree, the __user attribute is getting lost here and we're operating
on user buffers as if they were kernel buffers. That's a bug. Thanks,

Alex

> Otherwise, this is a good example driver. Thanks!
>
> > + }
> > +
> > + break;
> > +
> > + case VFIO_PCI_BAR0_REGION_INDEX ... VFIO_PCI_BAR5_REGION_INDEX:
> > + if (!mdev_state->region_info[index].start)
> > + mdev_read_base(mdev_state);
> > +
> > + if (is_write) {
> > + dump_buffer(buf, count);
> > +
> > +#if defined(DEBUG_REGS)
> > + pr_info("%s: BAR%d WR @0x%llx %s val:0x%02x dlab:%d\n",
> > + __func__, index, offset, wr_reg[offset],
> > + (u8)*buf, mdev_state->s[index].dlab);
> > +#endif
> > + handle_bar_write(index, mdev_state, offset, buf, count);
> > + } else {
> > + handle_bar_read(index, mdev_state, offset, buf, count);
> > + dump_buffer(buf, count);
> > +
> > +#if defined(DEBUG_REGS)
> > + pr_info("%s: BAR%d RD @0x%llx %s val:0x%02x dlab:%d\n",
> > + __func__, index, offset, rd_reg[offset],
> > + (u8)*buf, mdev_state->s[index].dlab);
> > +#endif
> > + }
> > + break;
> > +
> > + default:
> > + ret = -1;
> > + goto accessfailed;
> > + }
> > +
> > + ret = count;
> > +
> > +
> > +accessfailed:
> > + mutex_unlock(&mdev_state->ops_lock);
> > +
> > + return ret;
> > +}
> > +
> ...snip...
>
> > +ssize_t mtty_read(struct mdev_device *mdev, char __user *buf,
> > + size_t count, loff_t *ppos)
> > +{
> > + return mdev_access(mdev, buf, count, *ppos, false);
> > +}
> > +
> > +ssize_t mtty_write(struct mdev_device *mdev, const char __user *buf,
> > + size_t count, loff_t *ppos)
> > +{
> > + return mdev_access(mdev, (char *)buf, count, *ppos, true);
> > +}
> > +
> ...snip...
>

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