[PATCH v3 0/2] drm: address potential UAF bugs with drm_master ptrs
Desmond Cheong Zhi Xi
desmondcheongzx at gmail.com
Sun Jun 20 11:03:25 UTC 2021
This patch series addresses potential use-after-free errors when dereferencing pointers to struct drm_master. These were identified after one such bug was caught by Syzbot in drm_getunique():
The series is broken up into two patches:
1. Implement a locked version of drm_is_current_master() function that's used within drm_auth.c.
2. Identify areas in drm_lease.c where pointers to struct drm_master are dereferenced, and ensure that the master pointers are not freed during use.
Changes in v2 -> v3:
- Patch 1: Move the definition of drm_is_current_master and the _locked version higher up in drm_auth.c to avoid needing a forward declaration of drm_is_current_master_locked. As suggested by Daniel Vetter.
- Patch 2: Instead of leaking drm_device.master_mutex into drm_lease.c to protect drm_master pointers, add a new drm_file_get_master() function that returns drm_file->master while increasing its reference count, to prevent drm_file->master from being freed. As suggested by Daniel Vetter.
Changes in v1 -> v2:
- Patch 2: Move the lock and assignment before the DRM_DEBUG_LEASE in drm_mode_get_lease_ioctl, as suggested by Emil Velikov.
Desmond Cheong Zhi Xi (2):
drm: add a locked version of drm_is_current_master
drm: protect drm_master pointers in drm_lease.c
drivers/gpu/drm/drm_auth.c | 73 +++++++++++++++++++++++++++----------
drivers/gpu/drm/drm_lease.c | 57 ++++++++++++++++++++---------
include/drm/drm_auth.h | 1 +
include/drm/drm_file.h | 15 ++++++--
4 files changed, 107 insertions(+), 39 deletions(-)
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