From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22B5AC10F11 for ; Wed, 24 Apr 2019 17:14:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E30EC218B0 for ; Wed, 24 Apr 2019 17:14:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126066; bh=QmKis2BFlJaQlCBpe0IcKs28bpLwZbS6jofxw87qRpU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=M7YaN/8UB7GvE5nHSUQkrfz8oqrF033VgKEIcXsDpt6ZjkfwPHu8PVFOX2xW+ixek InEFNc+krC4jY2r/X+yGYPuXkL9g9R3wo0mc9QR+gF7bZ4nJHsULcEBZdbL1QHb3SP n0uBwnBTDMD5r1dVizIHuWhJyk9aJczN0sTnNse0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388066AbfDXROY (ORCPT ); Wed, 24 Apr 2019 13:14:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:38534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388055AbfDXROV (ORCPT ); Wed, 24 Apr 2019 13:14:21 -0400 Received: from localhost (62-193-50-229.as16211.net [62.193.50.229]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 94440218B0; Wed, 24 Apr 2019 17:14:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556126061; bh=QmKis2BFlJaQlCBpe0IcKs28bpLwZbS6jofxw87qRpU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Dog0Ax4mxH/UtjzBWFdrCrm5BdLEw/QzQevIMQTCMGmamyUoHJ5hpNCFkkjAitUF1 B0yiRDRm+a5p15hkVigtDStUHYJ4zYELm/3p3AR0nv8rY14hUk5BKZy3L7Pl31DCEQ IVFDHNNtF8r0NWgcZwdq26iKYsWBjelbIClR2TRg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Tolnay , Herbert Xu , Sasha Levin Subject: [PATCH 3.18 034/104] hwrng: virtio - Avoid repeated init of completion Date: Wed, 24 Apr 2019 19:08:51 +0200 Message-Id: <20190424170857.972033622@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190424170839.996641496@linuxfoundation.org> References: <20190424170839.996641496@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit aef027db48da56b6f25d0e54c07c8401ada6ce21 ] The virtio-rng driver uses a completion called have_data to wait for a virtio read to be fulfilled by the hypervisor. The completion is reset before placing a buffer on the virtio queue and completed by the virtio callback once data has been written into the buffer. Prior to this commit, the driver called init_completion on this completion both during probe as well as when registering virtio buffers as part of a hwrng read operation. The second of these init_completion calls should instead be reinit_completion because the have_data completion has already been inited by probe. As described in Documentation/scheduler/completion.txt, "Calling init_completion() twice on the same completion object is most likely a bug". This bug was present in the initial implementation of virtio-rng in f7f510ec1957 ("virtio: An entropy device, as suggested by hpa"). Back then the have_data completion was a single static completion rather than a member of one of potentially multiple virtrng_info structs as implemented later by 08e53fbdb85c ("virtio-rng: support multiple virtio-rng devices"). The original driver incorrectly used init_completion rather than INIT_COMPLETION to reset have_data during read. Tested by running `head -c48 /dev/random | hexdump` within crosvm, the Chrome OS virtual machine monitor, and confirming that the virtio-rng driver successfully produces random bytes from the host. Signed-off-by: David Tolnay Tested-by: David Tolnay Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- 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 72295ea2fd1c..5cdc8c534ad4 100644 --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -74,7 +74,7 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) if (!vi->busy) { vi->busy = true; - init_completion(&vi->have_data); + reinit_completion(&vi->have_data); register_buffer(vi, buf, size); } -- 2.19.1