From 0ea2ea42b31abc1141f2fd3911f952a97d401fcb Mon Sep 17 00:00:00 2001
From: Ezequiel Garcia <ezequiel@collabora.com>
Date: Mon, 27 Apr 2020 18:44:05 -0300
Subject: drm/vkms: Hold gem object while still in-use
Git-commit: 0ea2ea42b31abc1141f2fd3911f952a97d401fcb
Patch-mainline: v5.8-rc1
References: bsc#1113956
We need to keep the reference to the drm_gem_object
until the last access by vkms_dumb_create.
Therefore, the put the object after it is used.
This fixes a use-after-free issue reported by syzbot.
While here, change vkms_gem_create() symbol to static.
Reported-and-tested-by: syzbot+e3372a2afe1e7ef04bc7@syzkaller.appspotmail.com
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200427214405.13069-1-ezequiel@collabora.com
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/vkms/vkms_drv.h | 5 -----
drivers/gpu/drm/vkms/vkms_gem.c | 11 ++++++-----
2 files changed, 6 insertions(+), 10 deletions(-)
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -62,11 +62,6 @@ int vkms_output_init(struct vkms_device
struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev);
/* Gem stuff */
-struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
- struct drm_file *file,
- u32 *handle,
- u64 size);
-
int vkms_gem_fault(struct vm_fault *vmf);
int vkms_dumb_create(struct drm_file *file, struct drm_device *dev,
--- a/drivers/gpu/drm/vkms/vkms_gem.c
+++ b/drivers/gpu/drm/vkms/vkms_gem.c
@@ -93,10 +93,10 @@ int vkms_gem_fault(struct vm_fault *vmf)
return ret;
}
-struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
- struct drm_file *file,
- u32 *handle,
- u64 size)
+static struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
+ struct drm_file *file,
+ u32 *handle,
+ u64 size)
{
struct vkms_gem_object *obj;
int ret;
@@ -109,7 +109,6 @@ struct drm_gem_object *vkms_gem_create(s
return ERR_CAST(obj);
ret = drm_gem_handle_create(file, &obj->gem, handle);
- drm_gem_object_put_unlocked(&obj->gem);
if (ret)
return ERR_PTR(ret);
@@ -138,6 +137,8 @@ int vkms_dumb_create(struct drm_file *fi
args->size = gem_obj->size;
args->pitch = pitch;
+ drm_gem_object_put_unlocked(gem_obj);
+
DRM_DEBUG_DRIVER("Created object of size %lld\n", size);
return 0;