From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 5F2D21A024B for ; Tue, 10 Nov 2015 01:16:01 +1100 (AEDT) Date: Mon, 9 Nov 2015 16:12:04 +0100 From: Oleg Nesterov To: Andy Lutomirski Cc: "Amanieu d'Antras" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Linux MIPS Mailing List , linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "linux-s390@vger.kernel.org" , sparclinux@vger.kernel.org, Linux FS Devel , linux-arch , Linux API , Kenton Varda Subject: Re: [PATCH v2 00/20] Fix handling of compat_siginfo_t Message-ID: <20151109151204.GA10760@redhat.com> References: <1446684640-4112-1-git-send-email-amanieu@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 11/07, Andy Lutomirski wrote: > > On Wed, Nov 4, 2015 at 4:50 PM, Amanieu d'Antras wrote: > > One issue that isn't resolved in this series is sending signals between a 32-bit > > process and 64-bit process. Sending a si_int will work correctly, but a si_ptr > > value will likely get corrupted due to the different layouts of the 32-bit and > > 64-bit siginfo_t structures. > > This is so screwed up it's not even funny. Agreed, > A 64-bit big-endian compat calls rt_sigqueueinfo. It passes in (among > other things) a sigval_t. The kernel can choose to interpret it I always thought that the kernel should not interpret it at all. And indeed, copy_siginfo_to_user() does if (from->si_code < 0) return __copy_to_user(to, from, sizeof(siginfo_t)) probably copy_siginfo_to_user32() should do something similar, at least it should not truncate ->si_code it it is less than zero. Not sure what signalfd_copyinfo() should do. But perhaps I was wrong, I failed to find man sigqueueinfo, and man sigqueue() documents that it passes sigval_t. > BTW, x86 has its own set of screwups here. Somehow cr2 and error_code > ended up as part of ucontext instead of siginfo, which makes > absolutely no sense to me and bloats task_struct. Yes, and probably ->ip should have been the part of siginfo too. Say, if you get SIGBUS you can't trust sc->ip if another signal was dequeued before SIGBUS, in this case sc->ip will point to the handler of that another signal. That is why we have SYNCHRONOUS_MASK and it helps, but still this doesn't look nice. Oleg.