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authorDesmond Cheong Zhi Xi <desmondcheongzx@gmail.com>2021-07-12 07:35:08 +0300
committerDaniel Vetter <daniel.vetter@ffwll.ch>2021-07-20 21:22:19 +0300
commit56f0729a510f92151682ff6c89f69724d5595d6e (patch)
tree79227994f4b4c0df44486cdaa3e6edfec9cc02f8 /drivers/gpu/drm/drm_lease.c
parent0b0860a3cf5eccf183760b1177a1dcdb821b0b66 (diff)
downloadlinux-56f0729a510f92151682ff6c89f69724d5595d6e.tar.xz
drm: protect drm_master pointers in drm_lease.c
drm_file->master pointers should be protected by drm_device.master_mutex or drm_file.master_lookup_lock when being dereferenced. However, in drm_lease.c, there are multiple instances where drm_file->master is accessed and dereferenced while neither lock is held. This makes drm_lease.c vulnerable to use-after-free bugs. We address this issue in 2 ways: 1. Add a new drm_file_get_master() function that calls drm_master_get on drm_file->master while holding on to drm_file.master_lookup_lock. Since drm_master_get increments the reference count of master, this prevents master from being freed until we unreference it with drm_master_put. 2. In each case where drm_file->master is directly accessed and eventually dereferenced in drm_lease.c, we wrap the access in a call to the new drm_file_get_master function, then unreference the master pointer once we are done using it. Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20210712043508.11584-6-desmondcheongzx@gmail.com
Diffstat (limited to 'drivers/gpu/drm/drm_lease.c')
-rw-r--r--drivers/gpu/drm/drm_lease.c81
1 files changed, 61 insertions, 20 deletions
diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c
index 00fb433bcef1..92eac73d9001 100644
--- a/drivers/gpu/drm/drm_lease.c
+++ b/drivers/gpu/drm/drm_lease.c
@@ -106,10 +106,19 @@ static bool _drm_has_leased(struct drm_master *master, int id)
*/
bool _drm_lease_held(struct drm_file *file_priv, int id)
{
- if (!file_priv || !file_priv->master)
+ bool ret;
+ struct drm_master *master;
+
+ if (!file_priv)
return true;
- return _drm_lease_held_master(file_priv->master, id);
+ master = drm_file_get_master(file_priv);
+ if (!master)
+ return true;
+ ret = _drm_lease_held_master(master, id);
+ drm_master_put(&master);
+
+ return ret;
}
/**
@@ -128,13 +137,22 @@ bool drm_lease_held(struct drm_file *file_priv, int id)
struct drm_master *master;
bool ret;
- if (!file_priv || !file_priv->master || !file_priv->master->lessor)
+ if (!file_priv)
return true;
- master = file_priv->master;
+ master = drm_file_get_master(file_priv);
+ if (!master)
+ return true;
+ if (!master->lessor) {
+ ret = true;
+ goto out;
+ }
mutex_lock(&master->dev->mode_config.idr_mutex);
ret = _drm_lease_held_master(master, id);
mutex_unlock(&master->dev->mode_config.idr_mutex);
+
+out:
+ drm_master_put(&master);
return ret;
}
@@ -154,10 +172,16 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in)
int count_in, count_out;
uint32_t crtcs_out = 0;
- if (!file_priv || !file_priv->master || !file_priv->master->lessor)
+ if (!file_priv)
return crtcs_in;
- master = file_priv->master;
+ master = drm_file_get_master(file_priv);
+ if (!master)
+ return crtcs_in;
+ if (!master->lessor) {
+ crtcs_out = crtcs_in;
+ goto out;
+ }
dev = master->dev;
count_in = count_out = 0;
@@ -176,6 +200,9 @@ uint32_t drm_lease_filter_crtcs(struct drm_file *file_priv, uint32_t crtcs_in)
count_in++;
}
mutex_unlock(&master->dev->mode_config.idr_mutex);
+
+out:
+ drm_master_put(&master);
return crtcs_out;
}
@@ -489,7 +516,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
size_t object_count;
int ret = 0;
struct idr leases;
- struct drm_master *lessor = lessor_priv->master;
+ struct drm_master *lessor;
struct drm_master *lessee = NULL;
struct file *lessee_file = NULL;
struct file *lessor_file = lessor_priv->filp;
@@ -501,12 +528,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
if (!drm_core_check_feature(dev, DRIVER_MODESET))
return -EOPNOTSUPP;
- /* Do not allow sub-leases */
- if (lessor->lessor) {
- DRM_DEBUG_LEASE("recursive leasing not allowed\n");
- return -EINVAL;
- }
-
/* need some objects */
if (cl->object_count == 0) {
DRM_DEBUG_LEASE("no objects in lease\n");
@@ -518,12 +539,22 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
return -EINVAL;
}
+ lessor = drm_file_get_master(lessor_priv);
+ /* Do not allow sub-leases */
+ if (lessor->lessor) {
+ DRM_DEBUG_LEASE("recursive leasing not allowed\n");
+ ret = -EINVAL;
+ goto out_lessor;
+ }
+
object_count = cl->object_count;
object_ids = memdup_user(u64_to_user_ptr(cl->object_ids),
array_size(object_count, sizeof(__u32)));
- if (IS_ERR(object_ids))
- return PTR_ERR(object_ids);
+ if (IS_ERR(object_ids)) {
+ ret = PTR_ERR(object_ids);
+ goto out_lessor;
+ }
idr_init(&leases);
@@ -534,14 +565,15 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
if (ret) {
DRM_DEBUG_LEASE("lease object lookup failed: %i\n", ret);
idr_destroy(&leases);
- return ret;
+ goto out_lessor;
}
/* Allocate a file descriptor for the lease */
fd = get_unused_fd_flags(cl->flags & (O_CLOEXEC | O_NONBLOCK));
if (fd < 0) {
idr_destroy(&leases);
- return fd;
+ ret = fd;
+ goto out_lessor;
}
DRM_DEBUG_LEASE("Creating lease\n");
@@ -577,6 +609,7 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
/* Hook up the fd */
fd_install(fd, lessee_file);
+ drm_master_put(&lessor);
DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n");
return 0;
@@ -586,6 +619,8 @@ out_lessee:
out_leases:
put_unused_fd(fd);
+out_lessor:
+ drm_master_put(&lessor);
DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret);
return ret;
}
@@ -608,7 +643,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev,
struct drm_mode_list_lessees *arg = data;
__u32 __user *lessee_ids = (__u32 __user *) (uintptr_t) (arg->lessees_ptr);
__u32 count_lessees = arg->count_lessees;
- struct drm_master *lessor = lessor_priv->master, *lessee;
+ struct drm_master *lessor, *lessee;
int count;
int ret = 0;
@@ -619,6 +654,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev,
if (!drm_core_check_feature(dev, DRIVER_MODESET))
return -EOPNOTSUPP;
+ lessor = drm_file_get_master(lessor_priv);
DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id);
mutex_lock(&dev->mode_config.idr_mutex);
@@ -642,6 +678,7 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev,
arg->count_lessees = count;
mutex_unlock(&dev->mode_config.idr_mutex);
+ drm_master_put(&lessor);
return ret;
}
@@ -661,7 +698,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev,
struct drm_mode_get_lease *arg = data;
__u32 __user *object_ids = (__u32 __user *) (uintptr_t) (arg->objects_ptr);
__u32 count_objects = arg->count_objects;
- struct drm_master *lessee = lessee_priv->master;
+ struct drm_master *lessee;
struct idr *object_idr;
int count;
void *entry;
@@ -675,6 +712,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev,
if (!drm_core_check_feature(dev, DRIVER_MODESET))
return -EOPNOTSUPP;
+ lessee = drm_file_get_master(lessee_priv);
DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id);
mutex_lock(&dev->mode_config.idr_mutex);
@@ -702,6 +740,7 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev,
arg->count_objects = count;
mutex_unlock(&dev->mode_config.idr_mutex);
+ drm_master_put(&lessee);
return ret;
}
@@ -720,7 +759,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev,
void *data, struct drm_file *lessor_priv)
{
struct drm_mode_revoke_lease *arg = data;
- struct drm_master *lessor = lessor_priv->master;
+ struct drm_master *lessor;
struct drm_master *lessee;
int ret = 0;
@@ -730,6 +769,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev,
if (!drm_core_check_feature(dev, DRIVER_MODESET))
return -EOPNOTSUPP;
+ lessor = drm_file_get_master(lessor_priv);
mutex_lock(&dev->mode_config.idr_mutex);
lessee = _drm_find_lessee(lessor, arg->lessee_id);
@@ -750,6 +790,7 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev,
fail:
mutex_unlock(&dev->mode_config.idr_mutex);
+ drm_master_put(&lessor);
return ret;
}