From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by sourceware.org (Postfix) with ESMTPS id 9A94438438A3 for ; Fri, 8 Jan 2021 18:09:33 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 9A94438438A3 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=bp@suse.de 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 A723EAD29; Fri, 8 Jan 2021 18:09:32 +0000 (UTC) Date: Fri, 8 Jan 2021 19:09:35 +0100 From: Borislav Petkov To: "Chang S. Bae" Cc: tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org, len.brown@intel.com, dave.hansen@intel.com, hjl.tools@gmail.com, Dave.Martin@arm.com, jannh@google.com, mpe@ellerman.id.au, tony.luck@intel.com, ravi.v.shankar@intel.com, libc-alpha@sourceware.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/4] x86/signal: Prevent an alternate stack overflow before a signal delivery Message-ID: <20210108180935.GB12995@zn.tnic> References: <20201223015312.4882-1-chang.seok.bae@intel.com> <20201223015312.4882-4-chang.seok.bae@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20201223015312.4882-4-chang.seok.bae@intel.com> X-Spam-Status: No, score=-4.1 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 08 Jan 2021 18:09:34 -0000 On Tue, Dec 22, 2020 at 05:53:11PM -0800, Chang S. Bae wrote: > The kernel pushes data on the userspace stack when entering a signal. If > using a sigaltstack(), the kernel precisely knows the user stack size. ^^^^^^^^^^^^^^^^^^^^^^^ Formulate properly. > > When the kernel knows that the user stack is too small, avoid the overflow > and do an immediate SIGSEGV instead. ^^^^^^^^^^^^^^^^^^^^^^^ Ditto. > This overflow is known to occur on systems with large XSAVE state. The > effort to increase the size typically used for altstacks reduces the ^^^^^^^^^^ "alternate signal stacks" -- Regards/Gruss, Boris. SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg