On Thu, 27 Nov 2025 08:12:39 +0000 Akash Goel <[email protected]> wrote:
> 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. > > Co-developed-by: Boris Brezillon <[email protected]> > Signed-off-by: Akash Goel <[email protected]> Already approved privately, but here's the official Reviewed-by: Boris Brezillon <[email protected]> > --- > drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c > b/drivers/gpu/drm/panthor/panthor_sched.c > index b834123a6560..a6b8024e1a3c 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -779,6 +779,12 @@ 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 > * > @@ -3007,7 +3013,7 @@ 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; > @@ -3727,6 +3733,8 @@ 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: > @@ -3744,6 +3752,9 @@ 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; > @@ -3769,12 +3780,12 @@ 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; > @@ -3861,7 +3872,7 @@ 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;
