From patchwork Mon Aug 30 09:42:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mikulas Patocka X-Patchwork-Id: 12464817 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=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 B7269C432BE for ; Mon, 30 Aug 2021 09:42:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9808760F57 for ; Mon, 30 Aug 2021 09:42:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236237AbhH3Jn2 (ORCPT ); Mon, 30 Aug 2021 05:43:28 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48753 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236155AbhH3Jn0 (ORCPT ); Mon, 30 Aug 2021 05:43:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630316552; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=v6GpxVuNO75lRLYXPNvlemkGYv1U0FEo2sfLXlH03bo=; b=Oqevcop3+MXASRrL5lgNEyoDww3DAloUvxzBg0Ho2cisztoKnmkaUqRZ7d1guq6+gBxAwS 7mV3T4Y6AiHq4G/fbODrbcY3XeOkTznIb4z9DHJUi7I/CRBmc9Jk/9zM5jZlI8ezTih244 CgOpsTyXu6K0j2Jxr6dQCiPnJA4d+BE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-553-0IeoUDqxNVS73KDRI93tng-1; Mon, 30 Aug 2021 05:42:29 -0400 X-MC-Unique: 0IeoUDqxNVS73KDRI93tng-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BFA0A93920; Mon, 30 Aug 2021 09:42:28 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (file01.intranet.prod.int.rdu2.redhat.com [10.11.5.7]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9EBA760CA0; Mon, 30 Aug 2021 09:42:28 +0000 (UTC) Received: from file01.intranet.prod.int.rdu2.redhat.com (localhost [127.0.0.1]) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4) with ESMTP id 17U9gSQJ022895; Mon, 30 Aug 2021 05:42:28 -0400 Received: from localhost (mpatocka@localhost) by file01.intranet.prod.int.rdu2.redhat.com (8.14.4/8.14.4/Submit) with ESMTP id 17U9gRPq022891; Mon, 30 Aug 2021 05:42:28 -0400 X-Authentication-Warning: file01.intranet.prod.int.rdu2.redhat.com: mpatocka owned process doing -bs Date: Mon, 30 Aug 2021 05:42:27 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Helge Deller cc: "James E.J. Bottomley" , John David Anglin , linux-parisc Subject: [PATCH v2] parisc: fix crash with signals and alloca In-Reply-To: Message-ID: References: User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Sun, 29 Aug 2021, Helge Deller wrote: > > Index: linux-5.12/arch/parisc/kernel/signal.c > > =================================================================== > > --- linux-5.12.orig/arch/parisc/kernel/signal.c 2021-08-29 > > 19:06:33.000000000 +0200 > > +++ linux-5.12/arch/parisc/kernel/signal.c 2021-08-29 21:17:55.000000000 > > +0200 > > @@ -246,6 +246,11 @@ setup_rt_frame(struct ksignal *ksig, sig > > > > #ifdef CONFIG_64BIT > > > > + if (is_compat_task()) { > > + /* The gcc alloca implementation leaves garbage in the upper > > 32 bits of sp.*/ > > + frame = (struct rt_sigframe __user *)(unsigned > > long)ptr_to_compat(frame); > > + } > > + > > > Very good catch!!!! > I'm just wondering if we miss to clip the sp somewhere earlier in the > kernel call chain (e.g. in the irq/entry handlers), or if the clipping > should be done somewhere else, e.g. some lines above here... > > Helge You are right - we should clip earlier. I've realized that my patch wasn't correct - when we go down this path: get_sigframe -> sas_ss_flags -> on_sig_stack -> __on_sig_stack we already need clipped sp, so that __on_sig_stack can properly determine if we are on the signal stack or not. Here I'm sending a second version of the patch that clips the sp earlier: From: Mikulas Patocka I was debugging some crashes on parisc and I found out that there is a crash possibility if a function using alloca is interrupted by a signal. The reason for the crash is that the gcc alloca implementation leaves garbage in the upper 32 bits of the sp register. This normally doesn't matter (the upper bits are ignored because the PSW W-bit is clear), however the signal delivery routine in the kernel uses full 64 bits of sp and it fails with -EFAULT if the upper 32 bits are not zero. I created this program that demonstrates the problem: #include #include #include #include static __attribute__((noinline,noclone)) void aa(int *size) { void * volatile p = alloca(-*size); while (1) ; } static void handler(int sig) { write(1, "signal delivered\n", 17); _exit(0); } int main(void) { int size = -0x100; signal(SIGALRM, handler); alarm(1); aa(&size); } If you compile it with optimizations, it will crash. The "aa" function has this disassembly: 000106a0 : 106a0: 08 03 02 41 copy r3,r1 106a4: 08 1e 02 43 copy sp,r3 106a8: 6f c1 00 80 stw,ma r1,40(sp) 106ac: 37 dc 3f c1 ldo -20(sp),ret0 106b0: 0c 7c 12 90 stw ret0,8(r3) 106b4: 0f 40 10 9c ldw 0(r26),ret0 ; ret0 = 0x00000000FFFFFF00 106b8: 97 9c 00 7e subi 3f,ret0,ret0 ; ret0 = 0xFFFFFFFF0000013F 106bc: d7 80 1c 1a depwi 0,31,6,ret0 ; ret0 = 0xFFFFFFFF00000100 106c0: 0b 9e 0a 1e add,l sp,ret0,sp ; sp = 0xFFFFFFFFxxxxxxxx 106c4: e8 1f 1f f7 b,l,n 106c4 ,r0 This patch fixes the bug by truncating the "usp" variable to 32 bits. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org --- arch/parisc/kernel/signal.c | 6 ++++++ 1 file changed, 6 insertions(+) Index: linux-5.12/arch/parisc/kernel/signal.c =================================================================== --- linux-5.12.orig/arch/parisc/kernel/signal.c 2021-08-29 19:06:33.000000000 +0200 +++ linux-5.12/arch/parisc/kernel/signal.c 2021-08-30 11:21:12.000000000 +0200 @@ -237,6 +237,12 @@ setup_rt_frame(struct ksignal *ksig, sig #endif usp = (regs->gr[30] & ~(0x01UL)); +#ifdef CONFIG_64BIT + if (is_compat_task()) { + /* The gcc alloca implementation leaves garbage in the upper 32 bits of sp */ + usp = (compat_uint_t)usp; + } +#endif /*FIXME: frame_size parameter is unused, remove it. */ frame = get_sigframe(&ksig->ka, usp, sizeof(*frame));