accel/amdxdna: reject user command submission without a command BO

accel/amdxdna: reject user command submission without a command BO

amdxdna_drm_submit_execbuf() passes the user-supplied command BO handle
straight into amdxdna_cmd_submit() with drv_cmd == NULL. When the handle
is AMDXDNA_INVALID_BO_HANDLE (0), the block that fetches job->cmd_bo is
skipped, leaving it NULL, and no check rejects it on the user path (the
!job->cmd_bo guard lives inside the != INVALID branch).

The job is then armed and pushed to the DRM scheduler.
aie2_sched_job_run() takes the drv_cmd == NULL path and calls
amdxdna_cmd_set_state(job->cmd_bo) -> amdxdna_gem_vmap(NULL) ->
to_gobj(NULL)->dev, a NULL pointer dereference in the drm_sched worker.
A process with access to the accel node on a system with a probed AMD NPU
can trigger a kernel oops with a single AMDXDNA_EXEC_CMD ioctl
(cmd_handles = 0).

Only internal driver commands (SYNC_DEBUG_BO / ATTACH_DEBUG_BO)
legitimately pass AMDXDNA_INVALID_BO_HANDLE, and they always set drv_cmd.
Reject the invalid handle for user submissions (drv_cmd == NULL) at the
submit choke point so every user path is covered.

Fixes: aac243092b70 ("accel/amdxdna: Add command execution")
Cc: stable@vger.kernel.org
Found by 0sec automated security-research tooling (https://0sec.ai).
Assisted-by: 0sec:claude-opus-4-8
Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260713173030.87541-2-doruk@0sec.ai