Commit eec7e23d authored by Akash Goel's avatar Akash Goel Committed by Boris Brezillon
Browse files

drm/panthor: Prevent potential UAF in group creation 



This commit prevents the possibility of a use after free issue in the
GROUP_CREATE ioctl function, which arose as pointer to the group is
accessed in that ioctl function after storing it in the Xarray.
A malicious userspace can second guess the handle of a group and try
to call GROUP_DESTROY ioctl from another thread around the same time
as GROUP_CREATE ioctl.

To prevent the use after free exploit, this commit uses a mark on an
entry of group pool Xarray which is added just before returning from
the GROUP_CREATE ioctl function. The mark is checked for all ioctls
that specify the group handle and so userspace won't be abe to delete
a group that isn't marked yet.

v2: Add R-bs and fixes tags

Fixes: de854881 ("drm/panthor: Add the scheduler logical block")
Co-developed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: default avatarAkash Goel <akash.goel@arm.com>
Reviewed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Reviewed-by: default avatarChia-I Wu <olvaffe@gmail.com>
Link: https://patch.msgid.link/20251127164912.3788155-1-akash.goel@arm.com
parent 31d3354f

drivers/gpu/drm/panthor/panthor_sched.c

+15 −4
Original line number Diff line number Diff line
@@ -776,6 +776,12 @@ struct panthor_job_profiling_data { 
 */

#define MAX_GROUPS_PER_POOL 128



/*

 * Mark added on an entry of group pool Xarray to identify if the group has

 * been fully initialized and can be accessed elsewhere in the driver code.

 */

#define GROUP_REGISTERED XA_MARK_1



/**

 * struct panthor_group_pool - Group pool

 *
@@ -2906,7 +2912,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile) 
		return;



	xa_lock(&gpool->xa);

	xa_for_each(&gpool->xa, i, group) {

	xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {

		guard(spinlock)(&group->fdinfo.lock);

		pfile->stats.cycles += group->fdinfo.data.cycles;

		pfile->stats.time += group->fdinfo.data.time;
@@ -3591,6 +3597,8 @@ int panthor_group_create(struct panthor_file *pfile, 


	group_init_task_info(group);



	xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);



	return gid;



err_erase_gid:
@@ -3608,6 +3616,9 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle) 
	struct panthor_scheduler *sched = ptdev->scheduler;

	struct panthor_group *group;



	if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))

		return -EINVAL;



	group = xa_erase(&gpool->xa, group_handle);

	if (!group)

		return -EINVAL;
@@ -3633,12 +3644,12 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle) 
}



static struct panthor_group *group_from_handle(struct panthor_group_pool *pool,

					       u32 group_handle)

					       unsigned long group_handle)

{

	struct panthor_group *group;



	xa_lock(&pool->xa);

	group = group_get(xa_load(&pool->xa, group_handle));

	group = group_get(xa_find(&pool->xa, &group_handle, group_handle, GROUP_REGISTERED));

	xa_unlock(&pool->xa);



	return group;
@@ -3725,7 +3736,7 @@ panthor_fdinfo_gather_group_mem_info(struct panthor_file *pfile, 
		return;



	xa_lock(&gpool->xa);

	xa_for_each(&gpool->xa, i, group) {

	xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {

		stats->resident += group->fdinfo.kbo_sizes;

		if (group->csg_id >= 0)

			stats->active += group->fdinfo.kbo_sizes;