On 07/01/2019 08:56, Joonas Lahtinen wrote:

Add err goto label and use it when VMA can't be established or changes underneath.

Fixes: 1816f9236303 ("drm/i915: Support creation of unbound wc user mappings for objects") Reported-by: Adam Zabrocki adamza@microsoft.com Signed-off-by: Joonas 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

---

drivers/gpu/drm/i915/i915_gem.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index f1d594a53978..97cbc0e27e3e 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1738,6 +1738,9 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data, addr = vm_mmap(obj->base.filp, 0, args->size, PROT_READ | PROT_WRITE, MAP_SHARED, args->offset);

• if (IS_ERR((void *)addr))

• goto err;
  

• if (args->flags & I915_MMAP_WC) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma;

@@ -1753,17 +1756,22 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data, else addr = -ENOMEM; up_write(&mm->mmap_sem);

• if (IS_ERR((void *)addr))
  

• 	goto err;
  

/* This may race, but that's ok, it only gets set */ WRITE_ONCE(obj->frontbuffer_ggtt_origin, ORIGIN_CPU); } i915_gem_object_put(obj);

• if (IS_ERR((void *)addr))

• return addr;
  

args->addr_ptr = (uint64_t) addr; return 0;

+err:

• i915_gem_object_put(obj);
• return addr; }

static unsigned int tile_row_pages(const struct drm_i915_gem_object *obj)

Reviewed-by: Tvrtko Ursulin tvrtko.ursulin@intel.com

Regards,

Tvrtko

Thanks for the patch for both issues!

Best regards, Adam

-----Original Message----- From: Joonas Lahtinen joonas.lahtinen@linux.intel.com Sent: Thursday, February 7, 2019 5:39 AM To: Intel graphics driver community testing & development intel-gfx@lists.freedesktop.org Cc: stable@vger.kernel.org; Akash Goel akash.goel@intel.com; Chris Wilson chris@chris-wilson.co.uk; Tvrtko Ursulin tvrtko.ursulin@linux.intel.com; Adam Zabrocki adamza@microsoft.com Subject: Re: [PATCH 1/2] drm/i915: Prevent a race during I915_GEM_MMAP ioctl with WC set

Quoting Joonas Lahtinen (2019-01-07 10:56:55)

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.

These are now merged to drm-tip, and will head to 5.1 and then to stable kernels.

Thanks for the report and reviews!

Regards, Joonas

Fixes: 1816f9236303 ("drm/i915: Support creation of unbound wc user mappings for objects") Reported-by: Adam Zabrocki adamza@microsoft.com Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Joonas 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

---

drivers/gpu/drm/i915/i915_gem.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 062c8395557c..f1d594a53978 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1680,6 +1680,15 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data, return 0; } +static inline bool +match_gem_vma(struct vm_area_struct *vma, struct file *filp,

•         unsigned long addr, unsigned long size) {
  

•   return vma && vma->vm_file == filp &&
  

•          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.
  

@@ -1738,7 +1747,7 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data, return -EINTR; } vma = find_vma(mm, addr);

•           if (vma)
  

•           if (match_gem_vma(vma, obj->base.filp, addr, 
  

• args->size)) vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags)); else

-- 2.17.2