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drm/panthor: Prevent potential UAF in group creation

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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: de85488138 ("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>
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>
Link: https://patch.msgid.link/20251127164912.3788155-1-akash.goel@arm.com
This commit is contained in:
Akash Goel
2025-11-27 16:49:12 +00:00
committed by Boris Brezillon
parent 31d3354f42
commit eec7e23d84
1 changed files with 15 additions and 4 deletions
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19
drivers/gpu/drm/panthor/panthor_sched.c
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@@ -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;