[PATCH v3 4/9] drm: fix potential null ptr dereferences in drm_{auth,ioctl}
From: Desmond Cheong Zhi Xi <hidden>
Date: 2021-08-18 07:40:53
Also in:
dri-devel, intel-gfx, linux-kernel-mentees, lkml
Subsystem:
drm drivers, drm drivers and misc gpu patches, the rest · Maintainers:
David Airlie, Simona Vetter, Maarten Lankhorst, Maxime Ripard, Thomas Zimmermann, Linus Torvalds
There are three areas where we dereference struct drm_master without
checking if the pointer is non-NULL.
1. drm_getmagic is called from the ioctl_handler. Since
DRM_IOCTL_GET_MAGIC has no ioctl flags, drm_getmagic is run without
any check that drm_file.master has been set.
2. Similarly, drm_getunique is called from the ioctl_handler, but
DRM_IOCTL_GET_UNIQUE has no ioctl flags. So there is no guarantee that
drm_file.master has been set.
3. drm_master_release can also be called without having a
drm_file.master set. Here is one error path:
drm_open():
drm_open_helper():
drm_master_open():
drm_new_set_master(); <--- returns -ENOMEM,
drm_file.master not set
drm_file_free():
drm_master_release(); <--- NULL ptr dereference
(file_priv->master->magic_map)
Fix these by checking if the master pointers are NULL before use.
Signed-off-by: Desmond Cheong Zhi Xi <redacted>
---
drivers/gpu/drm/drm_auth.c | 16 ++++++++++++++--
drivers/gpu/drm/drm_ioctl.c | 5 +++++
2 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index f9267b21556e..b7230604496b 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c@@ -95,11 +95,18 @@ EXPORT_SYMBOL(drm_is_current_master); int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { struct drm_auth *auth = data; + struct drm_master *master; int ret = 0; mutex_lock(&dev->master_mutex); + master = file_priv->master; + if (!master) { + mutex_unlock(&dev->master_mutex); + return -EINVAL; + } + if (!file_priv->magic) { - ret = idr_alloc(&file_priv->master->magic_map, file_priv, + ret = idr_alloc(&master->magic_map, file_priv, 1, 0, GFP_KERNEL); if (ret >= 0) file_priv->magic = ret;
@@ -355,8 +362,12 @@ void drm_master_release(struct drm_file *file_priv) mutex_lock(&dev->master_mutex); master = file_priv->master; + + if (!master) + goto unlock; + if (file_priv->magic) - idr_remove(&file_priv->master->magic_map, file_priv->magic); + idr_remove(&master->magic_map, file_priv->magic); if (!drm_is_current_master_locked(file_priv)) goto out;
@@ -379,6 +390,7 @@ void drm_master_release(struct drm_file *file_priv) drm_master_put(&file_priv->master); spin_unlock(&dev->master_lookup_lock); } +unlock: mutex_unlock(&dev->master_mutex); }
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 26f3a9ede8fe..4d029d3061d9 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c@@ -121,6 +121,11 @@ int drm_getunique(struct drm_device *dev, void *data, mutex_lock(&dev->master_mutex); master = file_priv->master; + if (!master) { + mutex_unlock(&dev->master_mutex); + return -EINVAL; + } + if (u->unique_len >= master->unique_len) { if (copy_to_user(u->unique, master->unique, master->unique_len)) { mutex_unlock(&dev->master_mutex);
--
2.25.1