Messages in this thread |  | | From | Chia-I Wu <> | | Date | Thu, 27 Nov 2025 10:01:36 -0800 | | Subject | Re: [PATCH v2] drm/panthor: Prevent potential UAF in group creation |
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On Thu, Nov 27, 2025 at 9:09 AM Boris Brezillon <boris.brezillon@collabora.com> wrote: > > On Thu, 27 Nov 2025 16:49:12 +0000 > Akash Goel <akash.goel@arm.com> 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. > > > > v2: Add R-bs and fixes tags > > > > Fixes: de85488138247 ("drm/panthor: Add the scheduler logical block") > > Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com> > > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> > > to please checkpacth. > > > Signed-off-by: Akash Goel <akash.goel@arm.com> > > Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> > > Reviewed-by: Steven Price <steven.price@arm.com> Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Thanks! > > --- > > 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; >
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