From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4+I8JfW7XEZSe9NLHy9tK95Vlo/+kaogfzKoyExg6AMmlcrSsfGAEhawIza6yx/UtifhTD9 ARC-Seal: i=1; a=rsa-sha256; t=1523950401; cv=none; d=google.com; s=arc-20160816; b=oRtz/Bmo/3TyZNRZ/ptnLDb+lR7Kq1ntQmSytYohEUldqCKeWTu1CoWyVg5umwWAYK hrUfVLFjK1NkP3d0lvJ8J/sWryHvaX+ZGhq1Jqu7u3UlSRiI3JYwaS4MOBRRYpUbkGOs TXKRCP0FvubqpBiHBKnD8Ixd5x0r0TZXO4S/T1PX/BZlZrOL987WrjS/TD/AVp0qP+dO CboA0CxRLLfWCTSqSmnyRC/73Go5zf2rTQidrwH263M1gvtSbbG7ZPMUlz78e/A1+Xni X0bBL3cQJLCWYREw87hkVYFeq3sAqkc7w5dW/WB0wczxh2pAB+O09+SU/q0FmfoHADAi KA1Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject :delivered-to:delivered-to:list-id:list-subscribe:list-unsubscribe :list-help:list-post:precedence:mailing-list :arc-authentication-results; bh=jVpC9ORl8ZmJD+bkKK6nZ3zFrWG3jYNw/TIHmoFkqmc=; b=Oj3IhbxLxy6dXnp7Gbo+DnqzitLAtb3aSRCjfHDwgeHuUkMXlmG1JIAIM2m5H2D7HQ ajTwgE+THQdBNj1HAhyVx+qvyf38rNlEHd5xoOm/qGk+RPo2W1azCa45vHYY2ZRpy4uk tQXqSa7blpsKW8VvoMM1hRhGa0f33ffhO8CKC/qovOPK35kvmDM8ld4qMrNlkjnWGKyv AhPjeJqPRPo87VmGUnQO0u7Bopot0BpNO81vY6WIgv19Tl7arBioB8QDtY8A14ftQ572 TL4A4tdQsBu+daOcNrCk6TvxNndS82Yj2HcwNU9AROSebGFDn0GlOJcrEidqdN1KgKNZ iuZQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of kernel-hardening-return-13016-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13016-gregkh=linuxfoundation.org@lists.openwall.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of kernel-hardening-return-13016-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-13016-gregkh=linuxfoundation.org@lists.openwall.com Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: Subject: Re: [PATCH] x86/xen: Remove use of VLAs To: Boris Ostrovsky , Laura Abbott Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com References: <20180413221146.28476-1-labbott@redhat.com> <7cf66c00-74c2-62bb-81f5-4332313a5a6e@oracle.com> From: Juergen Gross Message-ID: Date: Tue, 17 Apr 2018 09:16:41 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <7cf66c00-74c2-62bb-81f5-4332313a5a6e@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1597670729617678421?= X-GMAIL-MSGID: =?utf-8?q?1597977816669499333?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 16/04/18 15:27, Boris Ostrovsky wrote: > On 04/13/2018 06:11 PM, Laura Abbott wrote: >> There's an ongoing effort to remove VLAs[1] from the kernel to eventually >> turn on -Wvla. The few VLAs in use have an upper bound based on a size >> of 64K. This doesn't produce an excessively large stack so just switch >> the upper bound. >> >> [1] https://lkml.org/lkml/2018/3/7/621 >> >> Signed-off-by: Laura Abbott >> --- >> arch/x86/xen/enlighten_pv.c | 6 ++---- >> 1 file changed, 2 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c >> index c36d23aa6c35..d96a5a535cbb 100644 >> --- a/arch/x86/xen/enlighten_pv.c >> +++ b/arch/x86/xen/enlighten_pv.c >> @@ -421,8 +421,7 @@ static void xen_load_gdt(const struct desc_ptr *dtr) >> { >> unsigned long va = dtr->address; >> unsigned int size = dtr->size + 1; >> - unsigned pages = DIV_ROUND_UP(size, PAGE_SIZE); > > > > Isn't dtr->size always either GDT_SIZE or 0? GDT_SIZE - 1 :-) >> - unsigned long frames[pages]; >> + unsigned long frames[DIV_ROUND_UP(SZ_64K, PAGE_SIZE)]; So we could just go with one frame and modify the BUG_ON() further below accordingly. Juergen