drm/i915: Sanity check mmap length against object size

ickle · ickle · commit 794a11cb6720 · 2019-03-18T12:58:15.000Z
We assumed that vm_mmap() would reject an attempt to mmap past the end of the filp (our object), but we were wrong. Applications that tried to use the mmap beyond the end of the object would be greeted by a SIGBUS. After this patch, those applications will be told about the error on creating the mmap, rather than at a random moment on later access. Reported-by: Antonio Argenziano <antonio.argenziano@intel.com> Testcase: igt/gem_mmap/bad-size Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Antonio Argenziano <antonio.argenziano@intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: stable@vger.kernel.org Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190314075829.16838-1-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
@@ -1639,8 +1639,13 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 	 * pages from.
 	 */
 	if (!obj->base.filp) {
-		i915_gem_object_put(obj);
-		return -ENXIO;
+		addr = -ENXIO;
+		goto err;
+	}
+
+	if (range_overflows(args->offset, args->size, (u64)obj->base.size)) {
+		addr = -EINVAL;
+		goto err;
 	}
 
 	addr = vm_mmap(obj->base.filp, 0, args->size,
@@ -1654,8 +1659,8 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 		struct vm_area_struct *vma;
 
 		if (down_write_killable(&mm->mmap_sem)) {
-			i915_gem_object_put(obj);
-			return -EINTR;
+			addr = -EINTR;
+			goto err;
 		}
 		vma = find_vma(mm, addr);
 		if (vma && __vma_matches(vma, obj->base.filp, addr, args->size))
@@ -1673,12 +1678,10 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 	i915_gem_object_put(obj);
 
 	args->addr_ptr = (u64)addr;
-
 	return 0;
 
 err:
 	i915_gem_object_put(obj);
-
 	return addr;
 }
 
