From eec7e23d848d2194dd8791fcd0f4a54d4378eecd Mon Sep 17 00:00:00 2001 From: Akash Goel Date: Thu, 27 Nov 2025 16:49:12 +0000 Subject: [PATCH] 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: de85488138247 ("drm/panthor: Add the scheduler logical block") Co-developed-by: Boris Brezillon Signed-off-by: Boris Brezillon Signed-off-by: Akash Goel Reviewed-by: Boris Brezillon Reviewed-by: Steven Price Reviewed-by: Chia-I Wu Link: https://patch.msgid.link/20251127164912.3788155-1-akash.goel@arm.com --- 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 e74ca071159d..5d2e9144d450 100644 --- a/drivers/gpu/drm/panthor/panthor_sched.c +++ b/drivers/gpu/drm/panthor/panthor_sched.c @@ -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; -- 2.47.3