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From: Daniel Vetter <daniel@ffwll.ch>
To: DRI Development <dri-devel@lists.freedesktop.org>
Cc: "Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"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>,
	linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
	"Niklas Schnelle" <schnelle@linux.ibm.com>,
	linux-s390@vger.kernel.org
Subject: Re: [PATCH 29/65] s390/pci: Remove races against pte updates
Date: Fri, 23 Oct 2020 14:26:02 +0200
Message-ID: <20201023122602.GB401619@phenom.ffwll.local> (raw)
In-Reply-To: <20201023122216.2373294-29-daniel.vetter@ffwll.ch>

On Fri, Oct 23, 2020 at 02:21:40PM +0200, 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 commit
> 3234ac664a87 ("/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're done. The write function also needs
> the copy_from_user move, since we can't take userspace faults while
> holding the mmap sem.
> 
> v2: Move VM_IO | VM_PFNMAP checks around so they keep returning EINVAL
> like before (Gerard)
> 
> v3: Polish commit message (Niklas)
> 
> Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> 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: 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
> Cc: Niklas Schnelle <schnelle@linux.ibm.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Apologies for this random patch bomb, typoed git send-email command :-/

v4 of this will come properly on Monday or so.
-Daniel

> ---
>  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;
>  	long ret;
>  
>  	if (!zpci_is_enabled())
> @@ -158,7 +140,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr,
>  	 * We only support write access to MIO capable devices if we are on
>  	 * a MIO enabled system. Otherwise we would have to check for every
>  	 * address if it is a special ZPCI_ADDR and would have to do
> -	 * a get_pfn() which we don't need for MIO capable devices.  Currently
> +	 * a pfn lookup which we don't need for MIO capable devices.  Currently
>  	 * ISM devices are the only devices without MIO support and there is no
>  	 * known need for accessing these from userspace.
>  	 */
> @@ -176,21 +158,37 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr,
>  	} else
>  		buf = local_buf;
>  
> -	ret = get_pfn(mmio_addr, VM_WRITE, &pfn);
> +	ret = -EFAULT;
> +	if (copy_from_user(buf, user_buffer, length))
> +		goto out_free;
> +
> +	mmap_read_lock(current->mm);
> +	ret = -EINVAL;
> +	vma = find_vma(current->mm, mmio_addr);
> +	if (!vma)
> +		goto out_unlock_mmap;
> +	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
> +		goto out_unlock_mmap;
> +	ret = -EACCES;
> +	if (!(vma->vm_flags & VM_WRITE))
> +		goto out_unlock_mmap;
> +
> +	ret = follow_pte_pmd(vma->vm_mm, mmio_addr, NULL, &ptep, NULL, &ptl);
>  	if (ret)
> -		goto out;
> -	io_addr = (void __iomem *)((pfn << PAGE_SHIFT) |
> +		goto out_unlock_mmap;
> +
> +	io_addr = (void __iomem *)((pte_pfn(*ptep) << PAGE_SHIFT) |
>  			(mmio_addr & ~PAGE_MASK));
>  
> -	ret = -EFAULT;
>  	if ((unsigned long) io_addr < ZPCI_IOMAP_ADDR_BASE)
> -		goto out;
> -
> -	if (copy_from_user(buf, user_buffer, length))
> -		goto out;
> +		goto out_unlock_pt;
>  
>  	ret = zpci_memcpy_toio(io_addr, buf, length);
> -out:
> +out_unlock_pt:
> +	pte_unmap_unlock(ptep, ptl);
> +out_unlock_mmap:
> +	mmap_read_unlock(current->mm);
> +out_free:
>  	if (buf != local_buf)
>  		kfree(buf);
>  	return ret;
> @@ -274,7 +272,9 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mmio_addr,
>  	u8 local_buf[64];
>  	void __iomem *io_addr;
>  	void *buf;
> -	unsigned long pfn;
> +	struct vm_area_struct *vma;
> +	pte_t *ptep;
> +	spinlock_t *ptl;
>  	long ret;
>  
>  	if (!zpci_is_enabled())
> @@ -287,7 +287,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mmio_addr,
>  	 * We only support read access to MIO capable devices if we are on
>  	 * a MIO enabled system. Otherwise we would have to check for every
>  	 * address if it is a special ZPCI_ADDR and would have to do
> -	 * a get_pfn() which we don't need for MIO capable devices.  Currently
> +	 * a pfn lookup which we don't need for MIO capable devices.  Currently
>  	 * ISM devices are the only devices without MIO support and there is no
>  	 * known need for accessing these from userspace.
>  	 */
> @@ -306,22 +306,38 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mmio_addr,
>  		buf = local_buf;
>  	}
>  
> -	ret = get_pfn(mmio_addr, VM_READ, &pfn);
> +	mmap_read_lock(current->mm);
> +	ret = -EINVAL;
> +	vma = find_vma(current->mm, mmio_addr);
> +	if (!vma)
> +		goto out_unlock_mmap;
> +	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
> +		goto out_unlock_mmap;
> +	ret = -EACCES;
> +	if (!(vma->vm_flags & VM_WRITE))
> +		goto out_unlock_mmap;
> +
> +	ret = follow_pte_pmd(vma->vm_mm, mmio_addr, NULL, &ptep, NULL, &ptl);
>  	if (ret)
> -		goto out;
> -	io_addr = (void __iomem *)((pfn << PAGE_SHIFT) | (mmio_addr & ~PAGE_MASK));
> +		goto out_unlock_mmap;
> +
> +	io_addr = (void __iomem *)((pte_pfn(*ptep) << PAGE_SHIFT) |
> +			(mmio_addr & ~PAGE_MASK));
>  
>  	if ((unsigned long) io_addr < ZPCI_IOMAP_ADDR_BASE) {
>  		ret = -EFAULT;
> -		goto out;
> +		goto out_unlock_pt;
>  	}
>  	ret = zpci_memcpy_fromio(buf, io_addr, length);
> -	if (ret)
> -		goto out;
> -	if (copy_to_user(user_buffer, buf, length))
> +
> +out_unlock_pt:
> +	pte_unmap_unlock(ptep, ptl);
> +out_unlock_mmap:
> +	mmap_read_unlock(current->mm);
> +
> +	if (!ret && copy_to_user(user_buffer, buf, length))
>  		ret = -EFAULT;
>  
> -out:
>  	if (buf != local_buf)
>  		kfree(buf);
>  	return ret;
> -- 
> 2.28.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20201021163242.1458885-1-daniel.vetter@ffwll.ch>
     [not found] ` <20201023122216.2373294-1-daniel.vetter@ffwll.ch>
2020-10-23 12:21   ` [PATCH 05/65] drm/atomic-helper: Add dma-fence annotations Daniel Vetter
2020-10-23 12:21   ` [PATCH 06/65] drm/vkms: Annotate vblank timer Daniel Vetter
2020-10-23 12:21   ` [PATCH 07/65] drm/vblank: Annotate with dma-fence signalling section Daniel Vetter
2020-10-23 12:21   ` [PATCH 08/65] drm/amdgpu: add dma-fence annotations to atomic commit path Daniel Vetter
2020-10-23 12:21   ` [PATCH 17/65] drm/scheduler: use dma-fence annotations in main thread Daniel Vetter
2020-10-23 12:21   ` [PATCH 18/65] drm/amdgpu: use dma-fence annotations in cs_submit() Daniel Vetter
2020-10-23 12:21   ` [PATCH 19/65] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code Daniel Vetter
2020-10-23 12:21   ` [PATCH 20/65] drm/scheduler: use dma-fence annotations in tdr work Daniel Vetter
2020-10-23 12:21   ` [PATCH 21/65] drm/amdgpu: use dma-fence annotations for gpu reset code Daniel Vetter
2020-10-23 12:21   ` [PATCH 22/65] Revert "drm/amdgpu: add fbdev suspend/resume on gpu reset" Daniel Vetter
2020-10-23 12:21   ` [PATCH 23/65] drm/i915: Annotate dma_fence_work Daniel Vetter
2020-10-23 12:21   ` [PATCH 29/65] s390/pci: Remove races against pte updates Daniel Vetter
2020-10-23 12:26     ` Daniel Vetter [this message]
2020-10-23 12:21   ` [PATCH 30/65] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-23 12:21   ` [PATCH 31/65] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-23 12:21   ` [PATCH 32/65] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-23 12:21   ` [PATCH 33/65] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-23 12:21   ` [PATCH 34/65] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-23 12:21   ` [PATCH 35/65] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-23 12:21   ` [PATCH 36/65] mm: Close race in generic_access_phys Daniel Vetter
2020-10-23 12:21   ` [PATCH 37/65] mm: Add unsafe_follow_pfn Daniel Vetter
2020-10-23 12:21   ` [PATCH 38/65] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-10-23 12:21   ` [PATCH 39/65] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-23 12:21   ` [PATCH 40/65] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-23 12:21   ` [PATCH 41/65] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-10-23 12:21   ` [PATCH 42/65] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-10-23 12:21   ` [PATCH 43/65] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-10-23 12:21   ` [PATCH 44/65] PCI: Revoke mappings like devmem Daniel Vetter

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