linux-kernel - [PATCH v1 1/1] platform/mellanox: fix potential race in mlxbf-tmfifo driver

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Message-ID: <b98c0ab61d644ba38fa9b3fd1607b138b0dd820b.1682518748.git.limings@nvidia.com>
Date:   Wed, 26 Apr 2023 10:23:44 -0400
From:   Liming Sun <limings@...dia.com>
To:     Vadim Pasternak <vadimp@...dia.com>,
        David Thompson <davthompson@...dia.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>
CC:     Liming Sun <limings@...dia.com>,
        <platform-driver-x86@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v1 1/1] platform/mellanox: fix potential race in mlxbf-tmfifo driver

This commit adds memory barrier for the 'vq' update in function
mlxbf_tmfifo_virtio_find_vqs() to avoid potential race due to
out-of-order memory write. It also adds barrier for the 'is_ready'
flag to make sure the initializations are visible before this flag
is checked.

Signed-off-by: Liming Sun <limings@...dia.com>
---
 drivers/platform/mellanox/mlxbf-tmfifo.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/mellanox/mlxbf-tmfifo.c b/drivers/platform/mellanox/mlxbf-tmfifo.c
index 91a077c35b8b..a79318e90a13 100644
--- a/drivers/platform/mellanox/mlxbf-tmfifo.c
+++ b/drivers/platform/mellanox/mlxbf-tmfifo.c
@@ -784,7 +784,7 @@ static void mlxbf_tmfifo_rxtx(struct mlxbf_tmfifo_vring *vring, bool is_rx)
 	fifo = vring->fifo;
 
 	/* Return if vdev is not ready. */
-	if (!fifo->vdev[devid])
+	if (!fifo || !fifo->vdev[devid])
 		return;
 
 	/* Return if another vring is running. */
@@ -980,9 +980,13 @@ static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
 
 		vq->num_max = vring->num;
 
+		vq->priv = vring;
+
+		/* Make vq update visible before using it. */
+		virtio_mb(false);
+
 		vqs[i] = vq;
 		vring->vq = vq;
-		vq->priv = vring;
 	}
 
 	return 0;
@@ -1302,6 +1306,9 @@ static int mlxbf_tmfifo_probe(struct platform_device *pdev)
 
 	mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
 
+	/* Make all updates visible before setting the 'is_ready' flag. */
+	virtio_mb(false);
+
 	fifo->is_ready = true;
 	return 0;
 
-- 
2.30.1