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Commit 6a204bd5 authored by Joonas Lahtinen's avatar Joonas Lahtinen Committed by Greg Kroah-Hartman
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drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set 



commit 2e7bd10e05afb866b5fb13eda25095c35d7a27cc upstream.

Make sure the underlying VMA in the process address space is the
same as it was during vm_mmap to avoid applying WC to wrong VMA.

A more long-term solution would be to have vm_mmap_locked variant
in linux/mmap.h for when caller wants to hold mmap_sem for an
extended duration.

v2:
- Refactor the compare function

Fixes: 1816f923 ("drm/i915: Support creation of unbound wc user mappings for objects")
Reported-by: default avatarAdam Zabrocki <adamza@microsoft.com>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <stable@vger.kernel.org> # v4.0+
Cc: Akash Goel <akash.goel@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Adam Zabrocki <adamza@microsoft.com>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20190207085454.10598-1-joonas.lahtinen@linux.intel.com


(cherry picked from commit 5c4604e757ba9b193b09768d75a7d2105a5b883f)
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4631e0b4

drivers/gpu/drm/i915/i915_gem.c

+11 −1
Original line number Diff line number Diff line
@@ -1821,6 +1821,16 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data, 
	return 0;

}



static inline bool

__vma_matches(struct vm_area_struct *vma, struct file *filp,

	      unsigned long addr, unsigned long size)

{

	if (vma->vm_file != filp)

		return false;



	return vma->vm_start == addr && (vma->vm_end - vma->vm_start) == size;

}



/**

 * i915_gem_mmap_ioctl - Maps the contents of an object, returning the address

 *			 it is mapped to.
@@ -1879,7 +1889,7 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data, 
			return -EINTR;

		}

		vma = find_vma(mm, addr);

		if (vma)

		if (vma && __vma_matches(vma, obj->base.filp, addr, args->size))

			vma->vm_page_prot =

				pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

		else