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[209.132.180.67]) by mx.google.com with ESMTP id y18si42238388pfk.16.2016.10.19.15.03.27; Wed, 19 Oct 2016 15:03:28 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754557AbcJSWDY (ORCPT + 27 others); Wed, 19 Oct 2016 18:03:24 -0400 Received: from mail-lf0-f53.google.com ([209.85.215.53]:36830 "EHLO mail-lf0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750763AbcJSWDW (ORCPT ); Wed, 19 Oct 2016 18:03:22 -0400 Received: by mail-lf0-f53.google.com with SMTP id b75so44857388lfg.3 for ; Wed, 19 Oct 2016 15:03:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=JTS0c1oOM7UW+GkF0CnjIcUZU4OfQ02DOGYJf1ldTNQ=; b=XCBt9T3YOg2Dw9hfFFsvSM3nxtVdG6I2zAl6rolVmIZWbnkoNTO+0nA0JL27CxFdce X5RjByDImyslQj7dpcbA97XpjhODuk3EsoZKVrndkVakUBMWgUUq7omWRoEaWQBAjVqI CvXXCr2Ftz+g3osq7+29j+RGtzU9wvZH+3rfzvJpuTQOiEfAbRGLF8ohlF0borVfyOkX 7NQfydlcBzY0cTGrGcGNMOL3CEitaXkoBpVn1xVpS77bfMwLL819ussRmJShc1C9vFuY 56hdUJN1xsaLHzB+a9rHsu6XG6MZUKYCRFfqQS1s5UqTD56+afqeGtwqLH/t3yZrvrOm h7HQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=JTS0c1oOM7UW+GkF0CnjIcUZU4OfQ02DOGYJf1ldTNQ=; b=mcKH4NcUE3KhCN36AQoSH/iw5gE6AISod7LnVF+lDwO++ShydWY+7mrO1iOccjUXf3 uNt9vPHbzqqK0/gImpUYjhho3NYe9yBy3kK+68xqpJgEstWcyiIgf5R7dQPr6GFW1Fm4 IvGfhFkM1ob3WdPM9SIg3C3PkDEZguy48nT9sL+OYjYIhq7Dobtoe/BCntqf3eAZENKw AJZG7aQRqOhwmwf/Hdy1Lmja7Kzo98f6T5bz3BSOttPWPL5mV3oLBOqx6B5tAsojS9nJ OMoDIIDxSB5BtsT22yZCv4wE+6MDZum5ekoDPOmVcMSDGJBOk+mj8a9Y8A2x7abGdJre Bfmg== X-Gm-Message-State: AA6/9Rkkwu2Rk7A6EiB6I5bounQC4zf4hcT101b5LMxAg02OdPzJhvsHOB6w2YMI+2+3dhaKFkqNKSNTHg7pOw== X-Received: by 10.194.28.166 with SMTP id c6mr6490871wjh.40.1476914600488; Wed, 19 Oct 2016 15:03:20 -0700 (PDT) MIME-Version: 1.0 Received: by 10.80.140.148 with HTTP; Wed, 19 Oct 2016 15:02:59 -0700 (PDT) In-Reply-To: References: From: Dmitry Safonov <0x7f454c46@gmail.com> Date: Thu, 20 Oct 2016 01:02:59 +0300 Message-ID: Subject: Re: x32 is broken in 4.9-rc1 due to "x86/signal: Add SA_{X32,IA32}_ABI sa_flags" To: Mikulas Patocka Cc: Dmitry Safonov , Oleg Nesterov , linux-mm@kvack.org, Cyrill Gorcunov , Pavel Emelyanov , Thomas Gleixner , open list Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2016-10-19 20:33 GMT+03:00 Mikulas Patocka : > > > On Wed, 19 Oct 2016, Mikulas Patocka wrote: > >> Hi >> >> In the kernel 4.9-rc1, the x32 support is seriously broken, a x32 process >> is killed with SIGKILL after returning from any signal handler. > > I should have said they are killed with SIGSEGV, not SIGKILL. > >> I use Debian sid x64-64 distribution with x32 architecture added from >> debian-ports. >> >> I bisected the bug and found out that it is caused by the patch >> 6846351052e685c2d1428e80ead2d7ca3d7ed913 ("x86/signal: Add >> SA_{X32,IA32}_ABI sa_flags"). >> >> example (strace of a process after receiving the SIGWINCH signal): >> >> epoll_wait(10, 0xef6890, 32, -1) = -1 EINTR (Interrupted system call) >> --- SIGWINCH {si_signo=SIGWINCH, si_code=SI_USER, si_pid=1772, si_uid=0} --- >> poll([{fd=4, events=POLLOUT}], 1, 0) = 1 ([{fd=4, revents=POLLOUT}]) >> write(4, "\0", 1) = 1 >> rt_sigreturn({mask=[INT QUIT ILL TRAP BUS KILL SEGV USR2 PIPE ALRM STKFLT TSTP TTOU URG XCPU XFSZ VTALRM IO PWR SYS RTMIN]}) = 0 >> --- SIGSEGV {si_signo=SIGSEGV, si_code=SI_KERNEL, si_addr=NULL} --- >> +++ killed by SIGSEGV +++ >> Neoprávnìný pøístup do pamìti (SIGSEGV) >> >> Mikulas > > BTW. when I take core dump of the killed x32 process, it shows: > > ELF Header: > Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 > Class: ELF32 > Data: 2's complement, little endian > Version: 1 (current) > OS/ABI: UNIX - System V > ABI Version: 0 > Type: CORE (Core file) > Machine: Intel 80386 > ^^^^^^^^^^^^^^^^^^^ > > So, the kernel somehow thinks that it is i386 process, not x32 process. A > core dump of a real x32 process shows "Class: ELF32, Machine: Advanced > Micro Devices X86-64". Hi Mikulas, could you give attached patch a shot? In about 10 hours I'll be at work and will have debian-x32 install, but for now, I can't test it. Thanks again on catching that. -- Dmitry Tested-by: Adam Borowski >From a546f8da1d12676fe79c746d859eb1e17aa4c331 Mon Sep 17 00:00:00 2001 From: Dmitry Safonov <0x7f454c46@gmail.com> Date: Thu, 20 Oct 2016 00:53:08 +0300 Subject: [PATCH] x86/signal: set SA_X32_ABI flag for x32 programs For x32 programs cs register is __USER_CS, so it returns here unconditionally - remove this check completely here. Fixes: commit 6846351052e6 ("x86/signal: Add SA_{X32,IA32}_ABI sa_flags") Reported-by: Mikulas Patocka Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com> --- arch/x86/kernel/signal_compat.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c index 40df33753bae..ec1f756f9dc9 100644 --- a/arch/x86/kernel/signal_compat.c +++ b/arch/x86/kernel/signal_compat.c @@ -105,9 +105,6 @@ void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact) /* Don't let flags to be set from userspace */ act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI); - if (user_64bit_mode(current_pt_regs())) - return; - if (in_ia32_syscall()) act->sa.sa_flags |= SA_IA32_ABI; if (in_x32_syscall()) -- 2.10.0