From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965739Ab2B1QKs (ORCPT ); Tue, 28 Feb 2012 11:10:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37607 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753524Ab2B1QKq (ORCPT ); Tue, 28 Feb 2012 11:10:46 -0500 Date: Tue, 28 Feb 2012 17:02:57 +0100 From: Oleg Nesterov To: Will Drewry Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, kernel-hardening@lists.openwall.com, netdev@vger.kernel.org, x86@kernel.org, arnd@arndb.de, davem@davemloft.net, hpa@zytor.com, mingo@redhat.com, peterz@infradead.org, rdunlap@xenotime.net, mcgrathr@chromium.org, tglx@linutronix.de, luto@mit.edu, eparis@redhat.com, serge.hallyn@canonical.com, djm@mindrot.org, scarybeasts@gmail.com, indan@nul.nu, pmoore@redhat.com, akpm@linux-foundation.org, corbet@lwn.net, eric.dumazet@gmail.com, markus@chromium.org, coreyb@linux.vnet.ibm.com, keescook@chromium.org Subject: Re: [PATCH v11 08/12] signal, x86: add SIGSYS info and make it synchronous. Message-ID: <20120228160257.GB3664@redhat.com> References: <1330140111-17201-1-git-send-email-wad@chromium.org> <1330140111-17201-8-git-send-email-wad@chromium.org> <20120227172208.GC10608@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/27, Will Drewry wrote: > > On Mon, Feb 27, 2012 at 11:22 AM, Oleg Nesterov wrote: > > On 02/24, Will Drewry wrote: > >> > >> To ensure that SIGSYS delivery occurs on return from the triggering > >> system call, SIGSYS is added to the SYNCHRONOUS_MASK macro. > > > > Hmm. Can't understand... please help. > > > >>  #define SYNCHRONOUS_MASK \ > >>       (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \ > >> -      sigmask(SIGTRAP) | sigmask(SIGFPE)) > >> +      sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS)) > > > > Why? > > > > SYNCHRONOUS_MASK just tells dequeue_signal() "pick them first". > > This is needed to make sure that the handler for, say SIGSEGV, > > can use ucontext->ip as a faulting addr. > > I think that Roland covered this. (Since the syscall_rollback was > called it's nice to let our handler get first go.) OK, except I do not really understand the "our handler get first go". Suppose SIGSYS "races" with the pending SIGHUP. With this change the caller for SIGHUP will be called first. But yes, setup_frame() will be called for SIGSYS first. Hopefully this is what you want. > > But seccomp adds info->si_call_addr, this looks unneeded. > > True enough. I can drop it. Hmm. I meant, the change in SYNCHRONOUS_MASK looks unneeded. Please keep ->si_call_addr, it is much more convenient than ucontext_t in userspace. > It'd only be useful if the SIGSYS wasn't > being forced and the signal was being handled without ucontext_t > access. No, force_ doesn't make any difference in this sense... In short, the patch looks fine to me, but if you resend it may be you can update the changelog. Oleg.