On Thu, 27 Nov 2025 16:02:15 +0000 Steven Price <[email protected]> wrote:
> On 27/11/2025 08:12, Akash Goel 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]> > > Reviewed-by: Steven Price <[email protected]> > > I *think* this should have a... > > Fixes: d2624d90a0b7 ("drm/panthor: assign unique names to queues") > > ... as I don't believe it was a problem before the rearrangement that > happened there. Oh, yeah, I didn't notice the commit was missing a Fixes tag, and you're correct about the offending commit. > > Thanks, > Steve > > > --- > > 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; >
