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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 E1B29C43381 for ; Wed, 27 Mar 2019 18:33:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE22C204FD for ; Wed, 27 Mar 2019 18:33:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553711636; bh=J5KM3Gz8B7BYdGn1fiYz+A1YR240YxFGAk4JGLcdUWU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=l1VsOtNNETwN/VhvRXmTm30FPJd3dqCFN0oDm21zqMTOct4v1hJgtnaleQr1fjRx0 x5Z76yNPpucHuDxbb4gWiJW4etWOZXcX+kQXqSusjCDk06u13BPPkBDpPXd50Q/pPi T6njDIFnvS7XxB3Hrg/DgJ322iXcvIJ8K9dKmHCk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404087AbfC0SZE (ORCPT ); Wed, 27 Mar 2019 14:25:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:44022 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404071AbfC0SZA (ORCPT ); Wed, 27 Mar 2019 14:25:00 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B3B862063F; Wed, 27 Mar 2019 18:24:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553711099; bh=J5KM3Gz8B7BYdGn1fiYz+A1YR240YxFGAk4JGLcdUWU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rpfiFuOQMMw3juGiaAY8oxcA0wN4iVXjhD1GuYK2CFJ/Vt6bKST2qLWunIL5LJbvD 74LB/fuBs2i7BgCFIRe5ALLcnPhuYlQbs1Ha87St0xRoaGoii7FtgiABADZwPHdgbH xCmB2mWK0Zzc/xAfZ0OI7dXEU+0kRpXgrn6JIRRw= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: David Tolnay , Herbert Xu , Sasha Levin , linux-crypto@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 52/63] hwrng: virtio - Avoid repeated init of completion Date: Wed, 27 Mar 2019 14:23:12 -0400 Message-Id: <20190327182323.18577-52-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190327182323.18577-1-sashal@kernel.org> References: <20190327182323.18577-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Tolnay [ 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 3fa2f8a009b3..1c5c4314c6b5 100644 --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -73,7 +73,7 @@ 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