Re: [PATCH v2] dma-mapping: use vmalloc_to_page for vmalloc addresses

From: Roman Skakun <rm.skakun@gmail.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Juergen Gross <jgross@suse.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	xen-devel@lists.xenproject.org, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
	Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
	Volodymyr Babchuk <volodymyr_babchuk@epam.com>,
	Roman Skakun <roman_skakun@epam.com>,
	Andrii Anisov <andrii_anisov@epam.com>
Subject: Re: [PATCH v2] dma-mapping: use vmalloc_to_page for vmalloc addresses
Date: Thu, 15 Jul 2021 10:39:38 +0300	[thread overview]
Message-ID: <CADu_u-OMx6Pj4DQDoOsdh6aNAzYys-+R=o+OzHYtLm=nECgkyQ@mail.gmail.com> (raw)
In-Reply-To: <YO4si0to/XYximwM@fedora>

> This looks like it wasn't picked up? Should it go in rc1?

Hi, Konrad!

This looks like an unambiguous bug, and should be in rc1.

Cheers!

ср, 14 июл. 2021 г. в 03:15, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>:
>
> On Tue, Jun 22, 2021 at 04:34:14PM +0300, Roman Skakun wrote:
> > This commit is dedicated to fix incorrect conversion from
> > cpu_addr to page address in cases when we get virtual
> > address which allocated in the vmalloc range.
> > As the result, virt_to_page() cannot convert this address
> > properly and return incorrect page address.
> >
> > Need to detect such cases and obtains the page address using
> > vmalloc_to_page() instead.
> >
> > Signed-off-by: Roman Skakun <roman_skakun@epam.com>
> > Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
> > ---
> > Hey!
> > Thanks for suggestions, Christoph!
> > I updated the patch according to your advice.
> > But, I'm so surprised because nobody catches this problem
> > in the common code before. It looks a bit strange as for me.
>
> This looks like it wasn't picked up? Should it go in rc1?
> >
> >
> >  kernel/dma/ops_helpers.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
> > index 910ae69cae77..782728d8a393 100644
> > --- a/kernel/dma/ops_helpers.c
> > +++ b/kernel/dma/ops_helpers.c
> > @@ -5,6 +5,14 @@
> >   */
> >  #include <linux/dma-map-ops.h>
> >
> > +static struct page *cpu_addr_to_page(void *cpu_addr)
> > +{
> > +     if (is_vmalloc_addr(cpu_addr))
> > +             return vmalloc_to_page(cpu_addr);
> > +     else
> > +             return virt_to_page(cpu_addr);
> > +}
> > +
> >  /*
> >   * Create scatter-list for the already allocated DMA buffer.
> >   */
> > @@ -12,7 +20,7 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
> >                void *cpu_addr, dma_addr_t dma_addr, size_t size,
> >                unsigned long attrs)
> >  {
> > -     struct page *page = virt_to_page(cpu_addr);
> > +     struct page *page = cpu_addr_to_page(cpu_addr);
> >       int ret;
> >
> >       ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
> > @@ -43,7 +51,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
> >               return -ENXIO;
> >
> >       return remap_pfn_range(vma, vma->vm_start,
> > -                     page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
> > +                     page_to_pfn(cpu_addr_to_page(cpu_addr)) + vma->vm_pgoff,
> >                       user_count << PAGE_SHIFT, vma->vm_page_prot);
> >  #else
> >       return -ENXIO;
> > --
> > 2.25.1
> >

-- 
Best Regards, Roman.