From patchwork Thu Sep 16 16:02:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 513613 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=-19.1 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_GIT 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 D3208C433F5 for ; Thu, 16 Sep 2021 17:44:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBA4D60C40 for ; Thu, 16 Sep 2021 17:44:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354491AbhIPRoW (ORCPT ); Thu, 16 Sep 2021 13:44:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:55270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354978AbhIPRky (ORCPT ); Thu, 16 Sep 2021 13:40:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5F66563245; Thu, 16 Sep 2021 16:52:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1631811121; bh=B+lmIPtsQ/2NkqwBSrlwIz/8L2llfIB2i2MRiu/q00A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=igzLBjuQ/ytpeoiPl+4WMDgRxQiZ37v7BWmMvD51BvURNwhpjixSVf1ARFMkyYTe/ mrARv80B1Olh5CYgenmS7LVP9DRdRR3Vqb4wbX0i2O6xWYnB3+NiRDqmCf3f8r675T sdYbiJVg5Sh+VF0zmsRuxljsoensu/H38UDFJ1Ao= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mikulas Patocka , Helge Deller Subject: [PATCH 5.14 391/432] parisc: fix crash with signals and alloca Date: Thu, 16 Sep 2021 18:02:20 +0200 Message-Id: <20210916155824.065590830@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210916155810.813340753@linuxfoundation.org> References: <20210916155810.813340753@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Mikulas Patocka commit 030f653078316a9cc9ca6bd1b0234dcf858be35d upstream. 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 Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- arch/parisc/kernel/signal.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/arch/parisc/kernel/signal.c +++ b/arch/parisc/kernel/signal.c @@ -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));