| Message ID | 20210323014656.10068-1-lyl2019@mail.ustc.edu.cn (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 52762efa2b256ed1c5274e5177cbd52ee11a2f6a |
| Headers | show |
| Series | gpu/xen: Fix a use after free in xen_drm_drv_init | expand |
Hi, good catch On 3/23/21 3:46 AM, Lv Yunlong wrote: > In function displback_changed, has the call chain > displback_connect(front_info)->xen_drm_drv_init(front_info). > We can see that drm_info is assigned to front_info->drm_info > and drm_info is freed in fail branch in xen_drm_drv_init(). > > Later displback_disconnect(front_info) is called and it calls > xen_drm_drv_fini(front_info) cause a use after free by > drm_info = front_info->drm_info statement. > > My patch has done two things. First fixes the fail label which > drm_info = kzalloc() failed and still free the drm_info. > Second sets front_info->drm_info to NULL to avoid uaf. > > Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn> Thank you for the patch, Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Will apply to drm-misc-next-fixes Thank you, Oleksandr > --- > drivers/gpu/drm/xen/xen_drm_front.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c > index 30d9adf31c84..9f14d99c763c 100644 > --- a/drivers/gpu/drm/xen/xen_drm_front.c > +++ b/drivers/gpu/drm/xen/xen_drm_front.c > @@ -521,7 +521,7 @@ static int xen_drm_drv_init(struct xen_drm_front_info *front_info) > drm_dev = drm_dev_alloc(&xen_drm_driver, dev); > if (IS_ERR(drm_dev)) { > ret = PTR_ERR(drm_dev); > - goto fail; > + goto fail_dev; > } > > drm_info->drm_dev = drm_dev; > @@ -551,8 +551,10 @@ static int xen_drm_drv_init(struct xen_drm_front_info *front_info) > drm_kms_helper_poll_fini(drm_dev); > drm_mode_config_cleanup(drm_dev); > drm_dev_put(drm_dev); > -fail: > +fail_dev: > kfree(drm_info); > + front_info->drm_info = NULL; > +fail: > return ret; > } >
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c index 30d9adf31c84..9f14d99c763c 100644 --- a/drivers/gpu/drm/xen/xen_drm_front.c +++ b/drivers/gpu/drm/xen/xen_drm_front.c @@ -521,7 +521,7 @@ static int xen_drm_drv_init(struct xen_drm_front_info *front_info) drm_dev = drm_dev_alloc(&xen_drm_driver, dev); if (IS_ERR(drm_dev)) { ret = PTR_ERR(drm_dev); - goto fail; + goto fail_dev; } drm_info->drm_dev = drm_dev; @@ -551,8 +551,10 @@ static int xen_drm_drv_init(struct xen_drm_front_info *front_info) drm_kms_helper_poll_fini(drm_dev); drm_mode_config_cleanup(drm_dev); drm_dev_put(drm_dev); -fail: +fail_dev: kfree(drm_info); + front_info->drm_info = NULL; +fail: return ret; }
In function displback_changed, has the call chain displback_connect(front_info)->xen_drm_drv_init(front_info). We can see that drm_info is assigned to front_info->drm_info and drm_info is freed in fail branch in xen_drm_drv_init(). Later displback_disconnect(front_info) is called and it calls xen_drm_drv_fini(front_info) cause a use after free by drm_info = front_info->drm_info statement. My patch has done two things. First fixes the fail label which drm_info = kzalloc() failed and still free the drm_info. Second sets front_info->drm_info to NULL to avoid uaf. Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn> --- drivers/gpu/drm/xen/xen_drm_front.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)