linux-kernel - [PATCH AUTOSEL 5.10 085/137] drm/amdkfd: fix circular locking on get_wave

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Date:   Tue,  6 Jul 2021 07:21:11 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jonathan Kim <jonathan.kim@....com>,
        Felix Kuehling <felix.kuehling@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.10 085/137] drm/amdkfd: fix circular locking on get_wave_state

From: Jonathan Kim <jonathan.kim@....com>

[ Upstream commit 63f6e01237257e7226efc5087f3f0b525d320f54 ]

get_wave_state acquires the mmap_lock on copy_to_user but so do
mmu_notifiers.  mmu_notifiers allows dqm locking so do get_wave_state
outside the dqm_lock to prevent circular locking.

v2: squash in unused variable removal.

Signed-off-by: Jonathan Kim <jonathan.kim@....com>
Reviewed-by: Felix Kuehling <felix.kuehling@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../drm/amd/amdkfd/kfd_device_queue_manager.c | 28 +++++++++----------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
index 6ea8a4b6efde..b971532e69eb 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
@@ -1677,29 +1677,27 @@ static int get_wave_state(struct device_queue_manager *dqm,
 			  u32 *save_area_used_size)
 {
 	struct mqd_manager *mqd_mgr;
-	int r;
 
 	dqm_lock(dqm);
 
-	if (q->properties.type != KFD_QUEUE_TYPE_COMPUTE ||
-	    q->properties.is_active || !q->device->cwsr_enabled) {
-		r = -EINVAL;
-		goto dqm_unlock;
-	}
-
 	mqd_mgr = dqm->mqd_mgrs[KFD_MQD_TYPE_CP];
 
-	if (!mqd_mgr->get_wave_state) {
-		r = -EINVAL;
-		goto dqm_unlock;
+	if (q->properties.type != KFD_QUEUE_TYPE_COMPUTE ||
+	    q->properties.is_active || !q->device->cwsr_enabled ||
+	    !mqd_mgr->get_wave_state) {
+		dqm_unlock(dqm);
+		return -EINVAL;
 	}
 
-	r = mqd_mgr->get_wave_state(mqd_mgr, q->mqd, ctl_stack,
-			ctl_stack_used_size, save_area_used_size);
-
-dqm_unlock:
 	dqm_unlock(dqm);
-	return r;
+
+	/*
+	 * get_wave_state is outside the dqm lock to prevent circular locking
+	 * and the queue should be protected against destruction by the process
+	 * lock.
+	 */
+	return mqd_mgr->get_wave_state(mqd_mgr, q->mqd, ctl_stack,
+			ctl_stack_used_size, save_area_used_size);
 }
 
 static int process_termination_cpsch(struct device_queue_manager *dqm,
-- 
2.30.2