drm/amdkfd: fix NULL dereference in get_queue_ids()

commit 2bd550b upstream.

When usr_queue_id_array is NULL and num_queues is non-zero,
get_queue_ids() returns NULL. The callers check only IS_ERR() on the
return value; since IS_ERR(NULL) == false the check passes, and
suspend_queues() calls q_array_invalidate() which immediately
dereferences NULL while iterating num_queues times.

Userspace can trigger this via kfd_ioctl_set_debug_trap() by supplying
num_queues > 0 with a zero queue_array_ptr, causing a kernel panic.

A NULL usr_queue_id_array with num_queues == 0 is a legitimate no-op
(q_array_invalidate never executes, and resume_queues already guards
all queue_ids dereferences behind a NULL check). Return ERR_PTR(-EINVAL)
only when num_queues is non-zero and the pointer is absent; both callers
already propagate IS_ERR() returns correctly to userspace.

Fixes: a70a93f ("drm/amdkfd: add debug suspend and resume process queues operation")
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f165a82)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Muhammad Bilal

drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c

@@ -3293,7 +3293,7 @@ static void copy_context_work_handler(struct work_struct *work)
 static uint32_t *get_queue_ids(uint32_t num_queues, uint32_t *usr_queue_id_array)
 {
 	if (!usr_queue_id_array)
-		return NULL;
+		return num_queues ? ERR_PTR(-EINVAL) : NULL;
 
 	if (num_queues > KFD_MAX_NUM_OF_QUEUES_PER_PROCESS)
 		return ERR_PTR(-EINVAL);