Re: [PATCH 4/4] remoteproc: qcom_q6v5_mss: Use a carveout to authenticate modem headers

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Tue, Dec 13, 2022 at 09:27:04PM +0530, Sibi Sankar wrote:
> Hey Robin,
> 
> Thanks for taking time to review the series.
> 
> On 12/13/22 20:37, Robin Murphy wrote:
> > On 2022-12-13 14:07, Sibi Sankar wrote:
> > > The memory region allocated using dma_alloc_attr with no kernel mapping
> > > attribute set would still be a part of the linear kernel map. Any access
> > > to this region by the application processor after assigning it to the
> > > remote Q6 will result in a XPU violation. Fix this by replacing the
> > > dynamically allocated memory region with a no-map carveout and unmap the
> > > modem metadata memory region before passing control to the remote Q6.
> > > 
> > > Reported-by: Amit Pundir <amit.pundir@linaro.org>
> > > Fixes: 6c5a9dc2481b ("remoteproc: qcom: Make secure world call for
> > > mem ownership switch")
> > > Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
> > > ---
> > > 
> > > The addition of the carveout and memunmap is required only on SoCs that
> > > mandate memory protection before transferring control to Q6, hence the
> > > driver falls back to dynamic memory allocation in the absence of the
> > > modem metadata carveout.
> > 
> > The DMA_ATTR_NO_KERNEL_MAPPING stuff is still broken and pointless, so
> > I'd expect to see this solution replacing it, not being added alongside.
> > It's just silly to say pass the "I don't need a CPU mapping" flag, then
> > manually open-code the same CPU mapping you would have got if you
> > hadn't, in a way that only works at all when a cacheable alias exists
> > anyway.
> 
> only a subset of SoCs supported by the driver are affected by
> the bug i.e. on the others dma_alloc_attr would still work
> without problems. I can perhaps drop the NO_KERNEL_MAPPING along
> with the vmap/vunmap and simplify things for those SoCs.
> 

Or perhaps revert fc156629b23a?

Thanks,
Mani

> - Sibi
> 
> > 
> > Thanks,
> > Robin.
> > 
> > >   drivers/remoteproc/qcom_q6v5_mss.c | 85 +++++++++++++++++++++---------
> > >   1 file changed, 61 insertions(+), 24 deletions(-)
> > > 
> > > diff --git a/drivers/remoteproc/qcom_q6v5_mss.c
> > > b/drivers/remoteproc/qcom_q6v5_mss.c
> > > index fddb63cffee0..8264275ecbd0 100644
> > > --- a/drivers/remoteproc/qcom_q6v5_mss.c
> > > +++ b/drivers/remoteproc/qcom_q6v5_mss.c
> > > @@ -211,6 +211,7 @@ struct q6v5 {
> > >       size_t mba_size;
> > >       size_t dp_size;
> > > +    phys_addr_t mdata_phys;
> > >       phys_addr_t mpss_phys;
> > >       phys_addr_t mpss_reloc;
> > >       size_t mpss_size;
> > > @@ -935,6 +936,7 @@ static int q6v5_mpss_init_image(struct q6v5
> > > *qproc, const struct firmware *fw,
> > >   {
> > >       unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS |
> > > DMA_ATTR_NO_KERNEL_MAPPING;
> > >       unsigned long flags = VM_DMA_COHERENT | VM_FLUSH_RESET_PERMS;
> > > +    void *mdata_region;
> > >       struct page **pages;
> > >       struct page *page;
> > >       dma_addr_t phys;
> > > @@ -951,34 +953,48 @@ static int q6v5_mpss_init_image(struct q6v5
> > > *qproc, const struct firmware *fw,
> > >       if (IS_ERR(metadata))
> > >           return PTR_ERR(metadata);
> > > -    page = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL,
> > > dma_attrs);
> > > -    if (!page) {
> > > -        kfree(metadata);
> > > -        dev_err(qproc->dev, "failed to allocate mdt buffer\n");
> > > -        return -ENOMEM;
> > > -    }
> > > +    if (qproc->mdata_phys) {
> > > +        mdata_region = memremap(qproc->mdata_phys, size, MEMREMAP_WC);
> > > +        if (!mdata_region) {
> > > +            dev_err(qproc->dev, "unable to map memory region:
> > > %pa+%zx\n",
> > > +                &qproc->mdata_phys, size);
> > > +            ret = -EBUSY;
> > > +            goto free_dma_attrs;
> > > +        }
> > > -    count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> > > -    pages = kmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
> > > -    if (!pages) {
> > > -        ret = -ENOMEM;
> > > -        goto free_dma_attrs;
> > > -    }
> > > +        memcpy(mdata_region, metadata, size);
> > > +        memunmap(mdata_region);
> > > +        phys = qproc->mdata_phys;
> > > +    } else {
> > > +        page = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL,
> > > dma_attrs);
> > > +        if (!page) {
> > > +            kfree(metadata);
> > > +            dev_err(qproc->dev, "failed to allocate mdt buffer\n");
> > > +            return -ENOMEM;
> > > +        }
> > > -    for (i = 0; i < count; i++)
> > > -        pages[i] = nth_page(page, i);
> > > +        count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> > > +        pages = kmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
> > > +        if (!pages) {
> > > +            ret = -ENOMEM;
> > > +            goto free_dma_attrs;
> > > +        }
> > > -    vaddr = vmap(pages, count, flags, pgprot_dmacoherent(PAGE_KERNEL));
> > > -    kfree(pages);
> > > -    if (!vaddr) {
> > > -        dev_err(qproc->dev, "unable to map memory region:
> > > %pa+%zx\n", &phys, size);
> > > -        ret = -EBUSY;
> > > -        goto free_dma_attrs;
> > > -    }
> > > +        for (i = 0; i < count; i++)
> > > +            pages[i] = nth_page(page, i);
> > > -    memcpy(vaddr, metadata, size);
> > > +        vaddr = vmap(pages, count, flags,
> > > pgprot_dmacoherent(PAGE_KERNEL));
> > > +        kfree(pages);
> > > +        if (!vaddr) {
> > > +            dev_err(qproc->dev, "unable to map memory region:
> > > %pa+%zx\n", &phys, size);
> > > +            ret = -EBUSY;
> > > +            goto free_dma_attrs;
> > > +        }
> > > -    vunmap(vaddr);
> > > +        memcpy(vaddr, metadata, size);
> > > +
> > > +        vunmap(vaddr);
> > > +    }
> > >       /* Hypervisor mapping to access metadata by modem */
> > >       mdata_perm = BIT(QCOM_SCM_VMID_HLOS);
> > > @@ -1008,7 +1024,8 @@ static int q6v5_mpss_init_image(struct q6v5
> > > *qproc, const struct firmware *fw,
> > >                "mdt buffer not reclaimed system may become unstable\n");
> > >   free_dma_attrs:
> > > -    dma_free_attrs(qproc->dev, size, page, phys, dma_attrs);
> > > +    if (!qproc->mdata_phys)
> > > +        dma_free_attrs(qproc->dev, size, page, phys, dma_attrs);
> > >       kfree(metadata);
> > >       return ret < 0 ? ret : 0;
> > > @@ -1882,6 +1899,26 @@ static int q6v5_alloc_memory_region(struct
> > > q6v5 *qproc)
> > >       qproc->mpss_phys = qproc->mpss_reloc = r.start;
> > >       qproc->mpss_size = resource_size(&r);
> > > +    if (!child) {
> > > +        node = of_parse_phandle(qproc->dev->of_node,
> > > "memory-region", 2);
> > > +    } else {
> > > +        child = of_get_child_by_name(qproc->dev->of_node, "metadata");
> > > +        node = of_parse_phandle(child, "memory-region", 0);
> > > +        of_node_put(child);
> > > +    }
> > > +
> > > +    if (!node)
> > > +        return 0;
> > > +
> > > +    ret = of_address_to_resource(node, 0, &r);
> > > +    of_node_put(node);
> > > +    if (ret) {
> > > +        dev_err(qproc->dev, "unable to resolve metadata region\n");
> > > +        return ret;
> > > +    }
> > > +
> > > +    qproc->mdata_phys = r.start;
> > > +
> > >       return 0;
> > >   }

-- 
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