This is a note to let you know that I've just added the patch titled
hwrng: virtio - don't wait on cleanup
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hwrng-virtio-don-t-wait-on-cleanup.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9c50a382f8e13e6db7abbe15241a4a9c88d4fc4e
Author: Laurent Vivier <lvivier@xxxxxxxxxx>
Date: Thu Oct 28 12:11:09 2021 +0200
hwrng: virtio - don't wait on cleanup
[ Upstream commit 2bb31abdbe55742c89f4dc0cc26fcbc8467364f6 ]
When virtio-rng device was dropped by the hwrng core we were forced
to wait the buffer to come back from the device to not have
remaining ongoing operation that could spoil the buffer.
But now, as the buffer is internal to the virtio-rng we can release
the waiting loop immediately, the buffer will be retrieve and use
when the virtio-rng driver will be selected again.
This avoids to hang on an rng_current write command if the virtio-rng
device is blocked by a lack of entropy. This allows to select
another entropy source if the current one is empty.
Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211028101111.128049-3-lvivier@xxxxxxxxxx
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Stable-dep-of: ac52578d6e8d ("hwrng: virtio - Fix race on data_avail and actual data")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index 999f523c80c1e..9a3fbd2b41107 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -94,6 +94,11 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
ret = wait_for_completion_killable(&vi->have_data);
if (ret < 0)
return ret;
+ /* if vi->data_avail is 0, we have been interrupted
+ * by a cleanup, but buffer stays in the queue
+ */
+ if (vi->data_avail == 0)
+ return read;
chunk = min_t(unsigned int, size, vi->data_avail);
memcpy(buf + read, vi->data, chunk);
@@ -117,7 +122,7 @@ static void virtio_cleanup(struct hwrng *rng)
struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
if (vi->busy)
- wait_for_completion(&vi->have_data);
+ complete(&vi->have_data);
}
static int probe_common(struct virtio_device *vdev)
