Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753403AbdFSTSv (ORCPT + 2 others); Mon, 19 Jun 2017 15:18:51 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:52243 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750950AbdFSSgK (ORCPT ); Mon, 19 Jun 2017 14:36:10 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Omar Sandoval , "Michael S . Tsirkin" , Ben Hutchings , Brad Spengler , Jiri Slaby , Willy Tarreau Subject: [PATCH 3.10 239/268] virtio-console: avoid DMA from stack Date: Mon, 19 Jun 2017 20:32:18 +0200 Message-Id: <1497897167-14556-240-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1497897167-14556-1-git-send-email-w@1wt.eu> References: <1497897167-14556-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Omar Sandoval commit c4baad50297d84bde1a7ad45e50c73adae4a2192 upstream. put_chars() stuffs the buffer it gets into an sg, but that buffer may be on the stack. This breaks with CONFIG_VMAP_STACK=y (for me, it manifested as printks getting turned into NUL bytes). Signed-off-by: Omar Sandoval Signed-off-by: Michael S. Tsirkin Reviewed-by: Amit Shah Cc: Ben Hutchings Cc: Brad Spengler Signed-off-by: Jiri Slaby Signed-off-by: Willy Tarreau --- drivers/char/virtio_console.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index ec3bd62..d69c63f 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1129,6 +1129,8 @@ static int put_chars(u32 vtermno, const char *buf, int count) { struct port *port; struct scatterlist sg[1]; + void *data; + int ret; if (unlikely(early_put_chars)) return early_put_chars(vtermno, buf, count); @@ -1137,8 +1139,14 @@ static int put_chars(u32 vtermno, const char *buf, int count) if (!port) return -EPIPE; - sg_init_one(sg, buf, count); - return __send_to_port(port, sg, 1, count, (void *)buf, false); + data = kmemdup(buf, count, GFP_ATOMIC); + if (!data) + return -ENOMEM; + + sg_init_one(sg, data, count); + ret = __send_to_port(port, sg, 1, count, data, false); + kfree(data); + return ret; } /* -- 2.8.0.rc2.1.gbe9624a