linux-kernel - [PATCH v2 1/1] drm/amdkfd: Create file descriptor after client is added to smi

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Date:   Thu, 31 Mar 2022 13:21:17 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     lee.jones@...aro.org
Cc:     linux-kernel@...r.kernel.org,
        Felix Kuehling <Felix.Kuehling@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH v2 1/1] drm/amdkfd: Create file descriptor after client is added to smi_clients list

This ensures userspace cannot prematurely clean-up the client before
it is fully initialised which has been proven to cause issues in the
past.

Cc: Felix Kuehling <Felix.Kuehling@....com>
Cc: Alex Deucher <alexander.deucher@....com>
Cc: "Christian König" <christian.koenig@....com>
Cc: "Pan, Xinhui" <Xinhui.Pan@....com>
Cc: David Airlie <airlied@...ux.ie>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: amd-gfx@...ts.freedesktop.org
Cc: dri-devel@...ts.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@...aro.org>
---

CAVEAT: This patch is completely untested
        I can't seem to find a configuration strategy to compile test this
        allyesconfig and allmodconfig do not appear sufficient

v2: Also remove Client from RCU list in error path

 drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c | 24 +++++++++++++--------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c
index e4beebb1c80a2..f2e1d506ba211 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c
@@ -247,15 +247,6 @@ int kfd_smi_event_open(struct kfd_dev *dev, uint32_t *fd)
 		return ret;
 	}
 
-	ret = anon_inode_getfd(kfd_smi_name, &kfd_smi_ev_fops, (void *)client,
-			       O_RDWR);
-	if (ret < 0) {
-		kfifo_free(&client->fifo);
-		kfree(client);
-		return ret;
-	}
-	*fd = ret;
-
 	init_waitqueue_head(&client->wait_queue);
 	spin_lock_init(&client->lock);
 	client->events = 0;
@@ -265,5 +256,20 @@ int kfd_smi_event_open(struct kfd_dev *dev, uint32_t *fd)
 	list_add_rcu(&client->list, &dev->smi_clients);
 	spin_unlock(&dev->smi_lock);
 
+	ret = anon_inode_getfd(kfd_smi_name, &kfd_smi_ev_fops, (void *)client,
+			       O_RDWR);
+	if (ret < 0) {
+		spin_lock(&dev->smi_lock);
+		list_del_rcu(&client->list);
+		spin_unlock(&dev->smi_lock);
+
+		synchronize_rcu();
+
+		kfifo_free(&client->fifo);
+		kfree(client);
+		return ret;
+	}
+	*fd = ret;
+
 	return 0;
 }
-- 
2.35.1.1021.g381101b075-goog