From patchwork Fri Sep 11 05:30:43 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?b?SsO8cmdlbiBHcm/Dnw==?= X-Patchwork-Id: 11769827 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 765991580 for ; Fri, 11 Sep 2020 05:32:38 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 560A12087C for ; Fri, 11 Sep 2020 05:32:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 560A12087C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kGbe4-000857-NI; Fri, 11 Sep 2020 05:30:48 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kGbe3-000852-Kp for xen-devel@lists.xenproject.org; Fri, 11 Sep 2020 05:30:47 +0000 X-Inumbo-ID: 041637f0-069f-4110-9499-3c88b1aa74dd Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 041637f0-069f-4110-9499-3c88b1aa74dd; Fri, 11 Sep 2020 05:30:46 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 40676B37D; Fri, 11 Sep 2020 05:31:01 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org Cc: Juergen Gross , Andrew Cooper , George Dunlap , Ian Jackson , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu Subject: [PATCH] xen/hypfs: fix writing of custom parameter Date: Fri, 11 Sep 2020 07:30:43 +0200 Message-Id: <20200911053043.29445-1-jgross@suse.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Today the maximum allowed data length for writing a hypfs node is tested in the generic hypfs_write() function. For custom runtime parameters this might be wrong, as the maximum allowed size is derived from the buffer holding the current setting, while there might be ways to set the parameter needing more characters than the minimal representation of that value. One example for this is the "ept" parameter. Its value buffer is sized to be able to hold the string "exec-sp=0" or "exec-sp=1", while it is allowed to use e.g. "no-exec-sp" or "exec-sp=yes" for setting it. Fix that by moving the length check one level down to the type specific write function. In order to avoid allocation of arbitrary sized buffers use a new MAX_PARAM_SIZE macro as an upper limit for custom writes. The value of MAX_PARAM_SIZE is the same as the limit in parse_params() for a single parameter. Fixes: 5b5ccafb0c42 ("xen: add basic hypervisor filesystem support") Reported-by: Andrew Cooper Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich --- xen/common/hypfs.c | 11 +++++++---- xen/common/kernel.c | 2 +- xen/include/xen/param.h | 3 +++ 3 files changed, 11 insertions(+), 5 deletions(-) diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c index b74c228191..8e932b5cf9 100644 --- a/xen/common/hypfs.c +++ b/xen/common/hypfs.c @@ -297,7 +297,9 @@ int hypfs_write_leaf(struct hypfs_entry_leaf *leaf, int ret; ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked); - ASSERT(ulen <= leaf->e.max_size); + + if ( ulen > leaf->e.max_size ) + return -ENOSPC; if ( leaf->e.type != XEN_HYPFS_TYPE_STRING && leaf->e.type != XEN_HYPFS_TYPE_BLOB && ulen != leaf->e.size ) @@ -356,6 +358,10 @@ int hypfs_write_custom(struct hypfs_entry_leaf *leaf, ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked); + /* Avoid oversized buffer allocation. */ + if ( ulen > MAX_PARAM_SIZE ) + return -ENOSPC; + buf = xzalloc_array(char, ulen); if ( !buf ) return -ENOMEM; @@ -386,9 +392,6 @@ static int hypfs_write(struct hypfs_entry *entry, ASSERT(entry->max_size); - if ( ulen > entry->max_size ) - return -ENOSPC; - l = container_of(entry, struct hypfs_entry_leaf, e); return entry->write(l, uaddr, ulen); diff --git a/xen/common/kernel.c b/xen/common/kernel.c index 9de07b7ac5..c3a943f077 100644 --- a/xen/common/kernel.c +++ b/xen/common/kernel.c @@ -57,7 +57,7 @@ static int assign_integer_param(const struct kernel_param *param, uint64_t val) static int parse_params(const char *cmdline, const struct kernel_param *start, const struct kernel_param *end) { - char opt[128], *optval, *optkey, *q; + char opt[MAX_PARAM_SIZE], *optval, *optkey, *q; const char *p = cmdline, *key; const struct kernel_param *param; int rc, final_rc = 0; diff --git a/xen/include/xen/param.h b/xen/include/xen/param.h index f4be944248..d0409d3a0e 100644 --- a/xen/include/xen/param.h +++ b/xen/include/xen/param.h @@ -26,6 +26,9 @@ struct kernel_param { } par; }; +/* Maximum length of a single parameter string. */ +#define MAX_PARAM_SIZE 128 + extern const struct kernel_param __setup_start[], __setup_end[]; #define __param(att) static const att \