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 C3DD4385AC12 for ; Tue, 16 Mar 2021 11:52:51 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org C3DD4385AC12 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 B988CAE56; Tue, 16 Mar 2021 11:52:50 +0000 (UTC) Date: Tue, 16 Mar 2021 12:52:48 +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, carlos@redhat.com, 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 v7 5/6] x86/signal: Detect and prevent an alternate signal stack overflow Message-ID: <20210316115248.GB18822@zn.tnic> References: <20210316065215.23768-1-chang.seok.bae@intel.com> <20210316065215.23768-6-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: <20210316065215.23768-6-chang.seok.bae@intel.com> X-Spam-Status: No, score=-4.5 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: Tue, 16 Mar 2021 11:52:53 -0000 On Mon, Mar 15, 2021 at 11:52:14PM -0700, Chang S. Bae wrote: > @@ -272,7 +275,8 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, > * If we are on the alternate signal stack and would overflow it, don't. > * Return an always-bogus address instead so we will die with SIGSEGV. > */ > - if (onsigstack && !likely(on_sig_stack(sp))) > + if (onsigstack && unlikely(sp <= current->sas_ss_sp || > + sp - current->sas_ss_sp > current->sas_ss_size)) > return (void __user *)-1L; So clearly I'm missing something because trying to trigger the test case in the bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=153531 on current tip/master doesn't work. Runs with MY_MINSIGSTKSZ under 2048 fail with: tst-minsigstksz-2: sigaltstack: Cannot allocate memory and above 2048 don't overwrite bytes below the stack. So something else is missing. How did you test this patch? Thx. -- Regards/Gruss, Boris. SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg