From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A9DF21773D for ; Wed, 9 Aug 2023 11:15:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C4F8C433C8; Wed, 9 Aug 2023 11:15:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691579741; bh=Loy1l09wQmN+xGENzRLkK1bK6n3Ih4AHIJfD5X4MVKk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ExjVyA5qhZO81UxPSoB3CJasIZrKVqex/YurJ0RlaI6mUWNbrHvPRQ9nBNs5kwxM2 kxW5oIuxSqD/Sh/SPTq2fjd94s0lksXGHkbl4uccDuLBy3Jb66iyWvDi7k63HslLqK ZNWMxtvTF1hTqTRAiogymOmftlZAQpxq6eK8PxWg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Laurent Vivier , "Michael S. Tsirkin" , Sasha Levin Subject: [PATCH 4.19 072/323] hwrng: virtio - add an internal buffer Date: Wed, 9 Aug 2023 12:38:30 +0200 Message-ID: <20230809103701.450413171@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230809103658.104386911@linuxfoundation.org> References: <20230809103658.104386911@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Laurent Vivier [ Upstream commit bf3175bc50a3754dc427e2f5046e17a9fafc8be7 ] hwrng core uses two buffers that can be mixed in the virtio-rng queue. If the buffer is provided with wait=0 it is enqueued in the virtio-rng queue but unused by the caller. On the next call, core provides another buffer but the first one is filled instead and the new one queued. And the caller reads the data from the new one that is not updated, and the data in the first one are lost. To avoid this mix, virtio-rng needs to use its own unique internal buffer at a cost of a data copy to the caller buffer. Signed-off-by: Laurent Vivier Link: https://lore.kernel.org/r/20211028101111.128049-2-lvivier@redhat.com Signed-off-by: Michael S. Tsirkin Stable-dep-of: ac52578d6e8d ("hwrng: virtio - Fix race on data_avail and actual data") Signed-off-by: Sasha Levin --- drivers/char/hw_random/virtio-rng.c | 43 ++++++++++++++++++++++------- 1 file changed, 33 insertions(+), 10 deletions(-) diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c index 7abd604e938c2..999f523c80c1e 100644 --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -30,13 +30,20 @@ static DEFINE_IDA(rng_index_ida); struct virtrng_info { struct hwrng hwrng; struct virtqueue *vq; - struct completion have_data; char name[25]; - unsigned int data_avail; int index; bool busy; bool hwrng_register_done; bool hwrng_removed; + /* data transfer */ + struct completion have_data; + unsigned int data_avail; + /* minimal size returned by rng_buffer_size() */ +#if SMP_CACHE_BYTES < 32 + u8 data[32]; +#else + u8 data[SMP_CACHE_BYTES]; +#endif }; static void random_recv_done(struct virtqueue *vq) @@ -51,14 +58,14 @@ static void random_recv_done(struct virtqueue *vq) } /* The host will fill any buffer we give it with sweet, sweet randomness. */ -static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size) +static void register_buffer(struct virtrng_info *vi) { struct scatterlist sg; - sg_init_one(&sg, buf, size); + sg_init_one(&sg, vi->data, sizeof(vi->data)); /* There should always be room for one buffer. */ - virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL); + virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL); virtqueue_kick(vi->vq); } @@ -67,6 +74,8 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) { int ret; struct virtrng_info *vi = (struct virtrng_info *)rng->priv; + unsigned int chunk; + size_t read; if (vi->hwrng_removed) return -ENODEV; @@ -74,19 +83,33 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) if (!vi->busy) { vi->busy = true; reinit_completion(&vi->have_data); - register_buffer(vi, buf, size); + register_buffer(vi); } if (!wait) return 0; - ret = wait_for_completion_killable(&vi->have_data); - if (ret < 0) - return ret; + read = 0; + while (size != 0) { + ret = wait_for_completion_killable(&vi->have_data); + if (ret < 0) + return ret; + + chunk = min_t(unsigned int, size, vi->data_avail); + memcpy(buf + read, vi->data, chunk); + read += chunk; + size -= chunk; + vi->data_avail = 0; + + if (size != 0) { + reinit_completion(&vi->have_data); + register_buffer(vi); + } + } vi->busy = false; - return vi->data_avail; + return read; } static void virtio_cleanup(struct hwrng *rng) -- 2.39.2