linux-kernel - [PATCH] hwrng: virtio - unregister device before reset

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Message-ID: <20211125180343.134505-1-mst@redhat.com>
Date:   Thu, 25 Nov 2021 13:04:11 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Laurent Vivier <lvivier@...hat.com>,
        Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        linux-crypto@...r.kernel.org
Subject: [PATCH] hwrng: virtio - unregister device before reset

unregister after reset is clearly wrong - device
can be used while it's reset. There's an attempt to
protect against that using hwrng_removed but it
seems racy since access can be in progress
when the flag is set.

Just unregister, then reset seems simpler and cleaner.
NB: we might be able to drop hwrng_removed in a follow-up patch.

Signed-off-by: Laurent Vivier <lvivier@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---

NB: lightly tested. Don't know much about rng. Any reviewers?


 drivers/char/hw_random/virtio-rng.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index b2bf78b25630..e856df7e285c 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -179,9 +179,9 @@ static void remove_common(struct virtio_device *vdev)
 	vi->data_avail = 0;
 	vi->data_idx = 0;
 	complete(&vi->have_data);
-	virtio_reset_device(vdev);
 	if (vi->hwrng_register_done)
 		hwrng_unregister(&vi->hwrng);
+	virtio_reset_device(vdev);
 	vdev->config->del_vqs(vdev);
 	ida_simple_remove(&rng_index_ida, vi->index);
 	kfree(vi);
-- 
MST