drm/i915: Handle vm_mmap error during I915_GEM_MMAP ioctl with WC set

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

v2:
- Dropping Fixes: as it's indeed impossible to race an object to the
  error address. (Chris)
v3:
- Use IS_ERR_VALUE (Chris)

Reported-by: Adam Zabrocki <adamza@microsoft.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.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: Tvrtko Ursulin <tvrtko.ursulin@intel.com> #v2
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190207085454.10598-2-joonas.lahtinen@linux.intel.com

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 2ea9b423de49c6e35123bf5446398966ea58430b..1d94bb61a779b181287a7169db25d48334961047 100644 (file)
--- 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_VALUE(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_VALUE(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 = (u64)addr;
 
        return 0;
+
+err:
+       i915_gem_object_put(obj);
+
+       return addr;
 }
 
 static unsigned int tile_row_pages(const struct drm_i915_gem_object *obj)