drm/msm: RCU-free the scheduler-containing ring and VM objects

Both struct msm_ringbuffer and struct msm_gem_vm embed a struct
drm_gpu_scheduler.  msm_ringbuffer_destroy() and the VM free callback
msm_gem_vm_free() call drm_sched_fini() on the embedded scheduler and then
free the containing object with plain kfree().

drm_sched_fence_get_timeline_name() returns fence->sched->name, and the
scheduler fence keeps a .release callback so it is not ops-detached on
signalling.  A finished fence exported to userspace (the submit out-fence, or
a VM_BIND fence, via sync_file / drm_syncobj) keeps pointing at the embedded
scheduler after the ring/VM is freed, so a later get_timeline_name() --
reachable unprivileged through SYNC_IOC_FILE_INFO -- dereferences freed slab
memory (KASAN slab-use-after-free read).

Per the dma-fence lifetime contract the exporter must keep the data backing a
signalled fence alive for an RCU grace period.  Free the scheduler-containing
objects with kfree_rcu() instead of kfree().

Fixes: 1d8a5ca436ee ("drm/msm: Conversion to drm scheduler")
Fixes: 92395af63a99 ("drm/msm: Add VM_BIND submitqueue")
Cc: stable@vger.kernel.org
Signed-off-by: Jonghyuk Kim(MalHyuk) <malhyuk97@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/750234/
Message-ID: <20260902012720.880783-1-malhyuk97@gmail.com>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>

0 files changed, 0 insertions, 0 deletions