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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"KVM list" <kvm@vger.kernel.org>, "Linux MM" <linux-mm@kvack.org>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	"Linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
	linux-s390 <linux-s390@vger.kernel.org>,
	"Daniel Vetter" <daniel.vetter@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>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH 10/13] PCI: revoke mappings like devmem
Date: Wed, 7 Oct 2020 20:24:48 -0300	[thread overview]
Message-ID: <20201007232448.GC5177@ziepe.ca> (raw)
In-Reply-To: <CAPcyv4hBL68A7CZa+YnooufDH2tevoxrx32DTJMQ6OHRnec7QQ@mail.gmail.com>

On Wed, Oct 07, 2020 at 12:33:06PM -0700, Dan Williams wrote:
> On Wed, Oct 7, 2020 at 11:11 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > the default for all driver uses.
> >
> > Except there's two more ways to access pci bars: sysfs and proc mmap
> > support. Let's plug that hole.
> 
> Ooh, yes, lets.
> 
> >
> > For revoke_devmem() to work we need to link our vma into the same
> > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > mapping we need to adjust vma->vm_file->f_mapping. Usually that's done
> > at ->open time, but that's a bit tricky here with all the entry points
> > and arch code. So instead create a fake file and adjust vma->vm_file.
> 
> I don't think you want to share the devmem inode for this, this should
> be based off the sysfs inode which I believe there is already only one
> instance per resource. In contrast /dev/mem can have multiple inodes
> because anyone can just mknod a new character device file, the same
> problem does not exist for sysfs.

The inode does not come from the filesystem char/mem.c creates a
singular anon inode in devmem_init_inode()

Seems OK to use this more widely, but it feels a bit weird to live in
char/memory.c.

This is what got me thinking maybe this needs to be a bit bigger
generic infrastructure - eg enter this scheme from fops mmap and
everything else is in mm/user_iomem.c

Jason

WARNING: multiple messages have this Message-ID
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-s390 <linux-s390@vger.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	"Jan Kara" <jack@suse.cz>, "Kees Cook" <keescook@chromium.org>,
	"KVM list" <kvm@vger.kernel.org>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	linux-pci@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Linux MM" <linux-mm@kvack.org>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	"Linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Subject: Re: [PATCH 10/13] PCI: revoke mappings like devmem
Date: Wed, 7 Oct 2020 20:24:48 -0300	[thread overview]
Message-ID: <20201007232448.GC5177@ziepe.ca> (raw)
In-Reply-To: <CAPcyv4hBL68A7CZa+YnooufDH2tevoxrx32DTJMQ6OHRnec7QQ@mail.gmail.com>

On Wed, Oct 07, 2020 at 12:33:06PM -0700, Dan Williams wrote:
> On Wed, Oct 7, 2020 at 11:11 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > the default for all driver uses.
> >
> > Except there's two more ways to access pci bars: sysfs and proc mmap
> > support. Let's plug that hole.
> 
> Ooh, yes, lets.
> 
> >
> > For revoke_devmem() to work we need to link our vma into the same
> > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > mapping we need to adjust vma->vm_file->f_mapping. Usually that's done
> > at ->open time, but that's a bit tricky here with all the entry points
> > and arch code. So instead create a fake file and adjust vma->vm_file.
> 
> I don't think you want to share the devmem inode for this, this should
> be based off the sysfs inode which I believe there is already only one
> instance per resource. In contrast /dev/mem can have multiple inodes
> because anyone can just mknod a new character device file, the same
> problem does not exist for sysfs.

The inode does not come from the filesystem char/mem.c creates a
singular anon inode in devmem_init_inode()

Seems OK to use this more widely, but it feels a bit weird to live in
char/memory.c.

This is what got me thinking maybe this needs to be a bit bigger
generic infrastructure - eg enter this scheme from fops mmap and
everything else is in mm/user_iomem.c

Jason

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-s390 <linux-s390@vger.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	"Jan Kara" <jack@suse.cz>, "Kees Cook" <keescook@chromium.org>,
	"KVM list" <kvm@vger.kernel.org>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	linux-pci@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Linux MM" <linux-mm@kvack.org>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	"Linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Subject: Re: [PATCH 10/13] PCI: revoke mappings like devmem
Date: Wed, 7 Oct 2020 20:24:48 -0300	[thread overview]
Message-ID: <20201007232448.GC5177@ziepe.ca> (raw)
In-Reply-To: <CAPcyv4hBL68A7CZa+YnooufDH2tevoxrx32DTJMQ6OHRnec7QQ@mail.gmail.com>

On Wed, Oct 07, 2020 at 12:33:06PM -0700, Dan Williams wrote:
> On Wed, Oct 7, 2020 at 11:11 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > the default for all driver uses.
> >
> > Except there's two more ways to access pci bars: sysfs and proc mmap
> > support. Let's plug that hole.
> 
> Ooh, yes, lets.
> 
> >
> > For revoke_devmem() to work we need to link our vma into the same
> > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > mapping we need to adjust vma->vm_file->f_mapping. Usually that's done
> > at ->open time, but that's a bit tricky here with all the entry points
> > and arch code. So instead create a fake file and adjust vma->vm_file.
> 
> I don't think you want to share the devmem inode for this, this should
> be based off the sysfs inode which I believe there is already only one
> instance per resource. In contrast /dev/mem can have multiple inodes
> because anyone can just mknod a new character device file, the same
> problem does not exist for sysfs.

The inode does not come from the filesystem char/mem.c creates a
singular anon inode in devmem_init_inode()

Seems OK to use this more widely, but it feels a bit weird to live in
char/memory.c.

This is what got me thinking maybe this needs to be a bit bigger
generic infrastructure - eg enter this scheme from fops mmap and
everything else is in mm/user_iomem.c

Jason
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

  parent reply	other threads:[~2020-10-07 23:24 UTC|newest]

Thread overview: 166+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-07 16:44 [PATCH 00/13] follow_pfn and other iomap races Daniel Vetter
2020-10-07 16:44 ` Daniel Vetter
2020-10-07 16:44 ` Daniel Vetter
2020-10-07 16:44 ` [PATCH 01/13] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 20:32   ` John Hubbard
2020-10-07 20:32     ` John Hubbard
2020-10-07 20:32     ` John Hubbard
2020-10-07 21:32     ` Daniel Vetter
2020-10-07 21:32       ` Daniel Vetter
2020-10-07 21:32       ` Daniel Vetter
2020-10-07 21:36       ` John Hubbard
2020-10-07 21:36         ` John Hubbard
2020-10-07 21:36         ` John Hubbard
2020-10-07 21:50         ` Daniel Vetter
2020-10-07 21:50           ` Daniel Vetter
2020-10-07 21:50           ` Daniel Vetter
2020-10-07 16:44 ` [PATCH 02/13] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 20:43   ` John Hubbard
2020-10-07 20:43     ` John Hubbard
2020-10-07 20:43     ` John Hubbard
2020-10-07 16:44 ` [PATCH 03/13] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 20:38   ` John Hubbard
2020-10-07 20:38     ` John Hubbard
2020-10-07 20:38     ` John Hubbard
2020-10-07 16:44 ` [PATCH 04/13] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 20:46   ` John Hubbard
2020-10-07 20:46     ` John Hubbard
2020-10-07 20:46     ` John Hubbard
2020-10-07 16:44 ` [PATCH 05/13] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:53   ` Jason Gunthorpe
2020-10-07 16:53     ` Jason Gunthorpe
2020-10-07 16:53     ` Jason Gunthorpe
2020-10-07 17:12     ` Daniel Vetter
2020-10-07 17:12       ` Daniel Vetter
2020-10-07 17:12       ` Daniel Vetter
2020-10-07 17:33       ` Jason Gunthorpe
2020-10-07 17:33         ` Jason Gunthorpe
2020-10-07 17:33         ` Jason Gunthorpe
2020-10-07 21:13   ` John Hubbard
2020-10-07 21:13     ` John Hubbard
2020-10-07 21:13     ` John Hubbard
2020-10-07 21:30     ` Daniel Vetter
2020-10-07 21:30       ` Daniel Vetter
2020-10-07 21:30       ` Daniel Vetter
2020-10-07 16:44 ` [PATCH 06/13] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 22:18   ` John Hubbard
2020-10-07 22:18     ` John Hubbard
2020-10-07 22:18     ` John Hubbard
2020-10-07 16:44 ` [PATCH 07/13] mm: close race in generic_access_phys Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 17:27   ` Jason Gunthorpe
2020-10-07 17:27     ` Jason Gunthorpe
2020-10-07 17:27     ` Jason Gunthorpe
2020-10-07 18:01     ` Daniel Vetter
2020-10-07 18:01       ` Daniel Vetter
2020-10-07 18:01       ` Daniel Vetter
2020-10-07 23:21       ` Jason Gunthorpe
2020-10-07 23:21         ` Jason Gunthorpe
2020-10-07 23:21         ` Jason Gunthorpe
2020-10-08  0:44   ` John Hubbard
2020-10-08  0:44     ` John Hubbard
2020-10-08  0:44     ` John Hubbard
2020-10-08  7:23     ` Daniel Vetter
2020-10-08  7:23       ` Daniel Vetter
2020-10-08  7:23       ` Daniel Vetter
2020-10-07 16:44 ` [PATCH 08/13] s390/pci: Remove races against pte updates Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-08 16:44   ` Gerald Schaefer
2020-10-08 16:44     ` Gerald Schaefer
2020-10-08 16:44     ` Gerald Schaefer
2020-10-08 17:16     ` Daniel Vetter
2020-10-08 17:16       ` Daniel Vetter
2020-10-08 17:16       ` Daniel Vetter
2020-10-07 16:44 ` [PATCH 09/13] PCI: obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 18:46   ` Bjorn Helgaas
2020-10-07 18:46     ` Bjorn Helgaas
2020-10-07 18:46     ` Bjorn Helgaas
2020-10-07 18:46     ` Bjorn Helgaas
2020-10-07 16:44 ` [PATCH 10/13] PCI: revoke mappings like devmem Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 18:41   ` Bjorn Helgaas
2020-10-07 18:41     ` Bjorn Helgaas
2020-10-07 18:41     ` Bjorn Helgaas
2020-10-07 19:24     ` Daniel Vetter
2020-10-07 19:24       ` Daniel Vetter
2020-10-07 19:24       ` Daniel Vetter
2020-10-07 19:33   ` Dan Williams
2020-10-07 19:33     ` Dan Williams
2020-10-07 19:33     ` Dan Williams
2020-10-07 19:47     ` Daniel Vetter
2020-10-07 19:47       ` Daniel Vetter
2020-10-07 19:47       ` Daniel Vetter
2020-10-07 22:23       ` Dan Williams
2020-10-07 22:23         ` Dan Williams
2020-10-07 22:23         ` Dan Williams
2020-10-07 22:29         ` Dan Williams
2020-10-07 22:29           ` Dan Williams
2020-10-07 22:29           ` Dan Williams
2020-10-08  8:09           ` Daniel Vetter
2020-10-08  8:09             ` Daniel Vetter
2020-10-08  8:09             ` Daniel Vetter
2020-10-07 23:24     ` Jason Gunthorpe [this message]
2020-10-07 23:24       ` Jason Gunthorpe
2020-10-07 23:24       ` Jason Gunthorpe
2020-10-08  7:31       ` Daniel Vetter
2020-10-08  7:31         ` Daniel Vetter
2020-10-08  7:31         ` Daniel Vetter
2020-10-08  7:49       ` Dan Williams
2020-10-08  7:49         ` Dan Williams
2020-10-08  7:49         ` Dan Williams
2020-10-08  8:13         ` Daniel Vetter
2020-10-08  8:13           ` Daniel Vetter
2020-10-08  8:13           ` Daniel Vetter
2020-10-08  8:35           ` Dan Williams
2020-10-08  8:35             ` Dan Williams
2020-10-08  8:35             ` Dan Williams
2020-10-08 12:41         ` Jason Gunthorpe
2020-10-08 12:41           ` Jason Gunthorpe
2020-10-08 12:41           ` Jason Gunthorpe
2020-10-07 16:44 ` [PATCH 11/13] mm: add unsafe_follow_pfn Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 17:36   ` Jason Gunthorpe
2020-10-07 17:36     ` Jason Gunthorpe
2020-10-07 17:36     ` Jason Gunthorpe
2020-10-07 18:10     ` Daniel Vetter
2020-10-07 18:10       ` Daniel Vetter
2020-10-07 18:10       ` Daniel Vetter
2020-10-07 19:00       ` Jason Gunthorpe
2020-10-07 19:00         ` Jason Gunthorpe
2020-10-07 19:00         ` Jason Gunthorpe
2020-10-07 19:38         ` Daniel Vetter
2020-10-07 19:38           ` Daniel Vetter
2020-10-07 19:38           ` Daniel Vetter
2020-10-07 16:44 ` [PATCH 12/13] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44 ` [PATCH 13/13] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 16:44   ` Daniel Vetter
2020-10-07 17:39   ` Jason Gunthorpe
2020-10-07 17:39     ` Jason Gunthorpe
2020-10-07 17:39     ` Jason Gunthorpe
2020-10-07 18:14     ` Daniel Vetter
2020-10-07 18:14       ` Daniel Vetter
2020-10-07 18:14       ` Daniel Vetter
2020-10-07 18:47       ` Jason Gunthorpe
2020-10-07 18:47         ` Jason Gunthorpe
2020-10-07 18:47         ` Jason Gunthorpe

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