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From: Daniel Vetter <daniel@ffwll.ch>
To: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: "Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kvm@vger.kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
	linux-s390@vger.kernel.org,
	"Gerald Schaefer" <gerald.schaefer@linux.ibm.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Jérôme Glisse" <jglisse@redhat.com>, "Jan Kara" <jack@suse.cz>
Subject: Re: [PATCH v2 08/17] s390/pci: Remove races against pte updates
Date: Mon, 12 Oct 2020 16:19:06 +0200
Message-ID: <20201012141906.GX438822@phenom.ffwll.local> (raw)
In-Reply-To: <6deb08dd-46f3-bf26-5362-fdc696f6fd74@linux.ibm.com>

On Mon, Oct 12, 2020 at 04:03:28PM +0200, Niklas Schnelle wrote:
> Hi Daniel,
> 
> freshly back from my vacation I've just taken a look at your patch.
> First thanks for this fix and the detailed commit description.
> Definitely makes sense to fix this and you can add my
> 
> Acked-by: Niklas Schnelle <schnelle@linux.ibm.com>
> 
> Content wise it all looks sane and clear and since Gerald did the testing,
> I would have applied it to our tree already, but I got some trivial
> checkpatch violations that probably apply to the whole series.
> I've commented them inline below.
> If you confirm there I can do the fixups when applying or you can resend.
> 
> On 10/9/20 9:59 AM, Daniel Vetter wrote:
> > Way back it was a reasonable assumptions that iomem mappings never
> > change the pfn range they point at. But this has changed:
> > 
> > - gpu drivers dynamically manage their memory nowadays, invalidating
> > ptes with unmap_mapping_range when buffers get moved
> > 
> > - contiguous dma allocations have moved from dedicated carvetouts to
> > cma regions. This means if we miss the unmap the pfn might contain
> > pagecache or anon memory (well anything allocated with GFP_MOVEABLE)
> > 
> > - even /dev/mem now invalidates mappings when the kernel requests that
> > iomem region when CONFIG_IO_STRICT_DEVMEM is set, see 3234ac664a87
> 
> The above commit mention should use the format
> 'commit 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims the region")'
> otherwise this results in a checkpatch ERROR.
> 
> > ("/dev/mem: Revoke mappings when a driver claims the region")
> > 
> > Accessing pfns obtained from ptes without holding all the locks is
> > therefore no longer a good idea. Fix this.
> > 
> > Since zpci_memcpy_from|toio seems to not do anything nefarious with
> > locks we just need to open code get_pfn and follow_pfn and make sure
> > we drop the locks only after we've done. The write function also needs
> 
> just a typo but just saw it "we're" instead of "we've"
> 
> > the copy_from_user move, since we can't take userspace faults while
> > holding the mmap sem.
> > 
> > Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> > 
> No empty line after the Revied-by tag.
> 
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> 
> Your Signed-off-by mail address does not match the one you're sending from,
> this yields a checkpatch warning when using git am with your mail.
> This is probably just a silly misconfiguration but since Signed-offs
> are signatures should I change this to 
> "Daniel Vetter <daniel.vetter@ffwll.ch>" which is the one you're
> sending from and also in the MAINTAINERS file?
> 
> 
> > Cc: Jason Gunthorpe <jgg@ziepe.ca>
> > Cc: Dan Williams <dan.j.williams@intel.com>
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: John Hubbard <jhubbard@nvidia.com>
> > Cc: Jérôme Glisse <jglisse@redhat.com>
> > Cc: Jan Kara <jack@suse.cz>
> > Cc: Dan Williams <dan.j.williams@intel.com>
> 
> The above Cc: line for Dan Williams is a duplicate
> 
> > Cc: linux-mm@kvack.org
> > Cc: linux-arm-kernel@lists.infradead.org
> > Cc: linux-samsung-soc@vger.kernel.org
> > Cc: linux-media@vger.kernel.org
> > Cc: Niklas Schnelle <schnelle@linux.ibm.com>
> > Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> > Cc: linux-s390@vger.kernel.org
> > --
> > v2: Move VM_IO | VM_PFNMAP checks around so they keep returning EINVAL
> > like before (Gerard)
> 
> I think the above should go before the CC/Signed-off/Reviewev block.

This is a per-subsystem bikeshed :-) drivers/gpu definitely wants it
above, but most core subsystems want it below. I'll move it.

> > ---
> >  arch/s390/pci/pci_mmio.c | 98 +++++++++++++++++++++++-----------------
> >  1 file changed, 57 insertions(+), 41 deletions(-)
> > 
> > diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c
> > index 401cf670a243..1a6adbc68ee8 100644
> > --- a/arch/s390/pci/pci_mmio.c
> > +++ b/arch/s390/pci/pci_mmio.c
> > @@ -119,33 +119,15 @@ static inline int __memcpy_toio_inuser(void __iomem *dst,
> >  	return rc;
> >  }
> >  
> > -static long get_pfn(unsigned long user_addr, unsigned long access,
> > -		    unsigned long *pfn)
> > -{
> > -	struct vm_area_struct *vma;
> > -	long ret;
> > -
> > -	mmap_read_lock(current->mm);
> > -	ret = -EINVAL;
> > -	vma = find_vma(current->mm, user_addr);
> > -	if (!vma)
> > -		goto out;
> > -	ret = -EACCES;
> > -	if (!(vma->vm_flags & access))
> > -		goto out;
> > -	ret = follow_pfn(vma, user_addr, pfn);
> > -out:
> > -	mmap_read_unlock(current->mm);
> > -	return ret;
> > -}
> > -
> >  SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr,
> >  		const void __user *, user_buffer, size_t, length)
> >  {
> >  	u8 local_buf[64];
> >  	void __iomem *io_addr;
> >  	void *buf;
> > -	unsigned long pfn;
> > +	struct vm_area_struct *vma;
> > +	pte_t *ptep;
> > +	spinlock_t *ptl;
> 
> With checkpatch.pl --strict the above yields a complained
> "CHECK: spinlock_t definition without comment" but I think
> that's really okay since your commit description is very clear.
> Same oin line 277.

I think this is a falls positive, checkpatch doesn't realize that
SYSCALL_DEFINE3 is a function, not a structure. And in a structure I'd
have added the kerneldoc or comment.

I'll fix up all the nits you've found for the next round. Thanks for
taking a look.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

  reply index

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09  7:59 [PATCH v2 00/17] follow_pfn and other iomap races Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 01/17] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-16  7:42   ` John Hubbard
2020-10-09  7:59 ` [PATCH v2 02/17] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 03/17] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-10 20:26   ` Oded Gabbay
2020-10-10 21:32     ` Daniel Vetter
2020-10-10 21:41       ` Daniel Vetter
2020-10-10 21:47         ` Oded Gabbay
2020-10-16  7:45   ` John Hubbard
2020-10-09  7:59 ` [PATCH v2 04/17] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 05/17] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-16  7:54   ` John Hubbard
2020-10-16  8:03     ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 06/17] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-09 10:14   ` Mauro Carvalho Chehab
2020-10-09 16:57     ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 07/17] mm: Close race in generic_access_phys Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 08/17] s390/pci: Remove races against pte updates Daniel Vetter
2020-10-12 14:03   ` Niklas Schnelle
2020-10-12 14:19     ` Daniel Vetter [this message]
2020-10-12 14:39       ` Niklas Schnelle
2020-10-21  7:55       ` Niklas Schnelle
2020-10-22  7:39         ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 09/17] mm: Add unsafe_follow_pfn Daniel Vetter
2020-10-09 10:34   ` Mauro Carvalho Chehab
2020-10-09 12:21     ` Jason Gunthorpe
2020-10-09 12:37       ` Mauro Carvalho Chehab
2020-10-09 12:39         ` Mauro Carvalho Chehab
2020-10-09 12:48         ` Jason Gunthorpe
2020-10-09 17:52           ` Daniel Vetter
2020-10-09 18:01             ` Jason Gunthorpe
2020-10-09 19:31               ` Daniel Vetter
2020-10-10  9:21             ` Mauro Carvalho Chehab
2020-10-10 10:53               ` Daniel Vetter
2020-10-10 11:39                 ` Mauro Carvalho Chehab
2020-10-10 11:56                   ` Daniel Vetter
2020-10-10 17:22             ` Tomasz Figa
2020-10-10 21:35               ` Laurent Pinchart
2020-10-10 21:50                 ` Daniel Vetter
2020-10-11  6:27                   ` Mauro Carvalho Chehab
2020-10-11  6:36                     ` Mauro Carvalho Chehab
2020-10-10 21:11             ` Laurent Pinchart
2020-10-12 10:46           ` Marek Szyprowski
2020-10-12 13:49             ` Daniel Vetter
2020-10-10 17:30         ` Tomasz Figa
2020-10-09  7:59 ` [PATCH v2 10/17] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-10-10  9:24   ` Mauro Carvalho Chehab
2020-10-09  7:59 ` [PATCH v2 11/17] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 12/17] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 13/17] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 14/17] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-10-09 10:59   ` Greg Kroah-Hartman
2020-10-09 12:31   ` Jason Gunthorpe
2020-10-09 14:24     ` Daniel Vetter
2020-10-09 14:32       ` Jason Gunthorpe
2020-10-09 18:28         ` Dan Williams
2020-10-15  0:09           ` Jason Gunthorpe
2020-10-15  7:52             ` Daniel Vetter
2020-10-15  7:55               ` Daniel Vetter
2020-10-15 15:29             ` Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 15/17] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-10-09 10:58   ` Greg Kroah-Hartman
2020-10-09  7:59 ` [PATCH v2 16/17] PCI: Revoke mappings like devmem Daniel Vetter
2020-10-09  7:59 ` [PATCH v2 17/17] drm/i915: Properly request PCI BARs Daniel Vetter
2020-10-09  9:47   ` Ville Syrjälä
2020-10-09 10:01     ` Daniel Vetter
2020-10-09 10:41       ` Ville Syrjälä
2020-10-09 14:18         ` Daniel Vetter

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