From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 405Rdr6dstzF0tM for ; Wed, 21 Mar 2018 08:58:40 +1100 (AEDT) Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w2KLnFap105123 for ; Tue, 20 Mar 2018 17:58:38 -0400 Received: from e06smtp13.uk.ibm.com (e06smtp13.uk.ibm.com [195.75.94.109]) by mx0b-001b2d01.pphosted.com with ESMTP id 2gu94uubg5-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Tue, 20 Mar 2018 17:58:37 -0400 Received: from localhost by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 20 Mar 2018 21:58:36 -0000 Date: Tue, 20 Mar 2018 14:58:28 -0700 From: Ram Pai To: Li Wang Cc: Michael Ellerman , Jan Stancek , ltp@lists.linux.it, linux-mm@kvack.org, "linuxppc-dev@lists.ozlabs.org" Subject: Re: [bug?] Access was denied by memory protection keys in execute-only address Reply-To: Ram Pai References: <871sguep4v.fsf@concordia.ellerman.id.au> <20180308164545.GM1060@ram.oc3035372033.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: Message-Id: <20180320215828.GA5825@ram.oc3035372033.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Mar 09, 2018 at 11:43:00AM +0800, Li Wang wrote: > On Fri, Mar 9, 2018 at 12:45 AM, Ram Pai <[1]linuxram@us.ibm.com> wrote: > > On Thu, Mar 08, 2018 at 11:19:12PM +1100, Michael Ellerman wrote: > > Li Wang <[2]liwang@redhat.com> writes: > > > Hi, > > > > > > ltp/mprotect04[1] crashed by SEGV_PKUERR on ppc64(LPAR on P730, > Power 8 > > > 8247-22L) with kernel-v4.16.0-rc4. > > > > > > 10000000-10020000 r-xp 00000000 fd:00 167223           mprotect04 > > > 10020000-10030000 r--p 00010000 fd:00 167223           mprotect04 > > > 10030000-10040000 rw-p 00020000 fd:00 167223           mprotect04 > > > 1001a380000-1001a3b0000 rw-p 00000000 00:00 0          [heap] > > > 7fffa6c60000-7fffa6c80000 --xp 00000000 00:00 0 ​ > > > > > > ​&exec_func = 0x10030170​ > > > > > > ​&func = 0x7fffa6c60170​ > > > > > > ​While perform ​ > > > "(*func)();" we get the > > > ​segmentation fault. > > > ​ > > > > > > ​strace log:​ > > > > > > ------------------- > > > ​mprotect(0x7fffaed00000, 131072, PROT_EXEC) = 0 > > > rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0 > > > --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_PKUERR, > si_addr=0x7fffaed00170} > > > ---​ > > > > Looks like a bug to me. > > > > Please Cc linuxppc-dev on powerpc bugs. > > > > I also can't reproduce this failure on my machine. > > Not sure what's going on? > > I could reproduce it on a power7 lpar.  But not on a power8 lpar. > > The problem seems to be that the cpu generates a key exception if > the page with Read/Write-disable-but-execute-enable key is executed > on power7. If I enable read on that key, the exception disappears. > > After adding read permission on that key, reproducer get PASS on my power8 > machine too.​ > ​(​mprotect(..,PROT_READ | PROT_EXEC))​ >   > > BTW: the testcase executes > ​​mprotect(..,PROT_EXEC). > The mprotect(, PROT_EXEC) system call internally generates a > execute-only key and associates it with the pages in the address-range.  > > Now since Li Wang claims that he can reproduce it on power8 as well, i > am wondering if the slightly different cpu behavior is dependent on the > version of the firmware/microcode? > > ​I also run this reproducer on series ppc kvm machines, but none of them > get the FAIL. > If you need some more HW info, pls let me know.​ Hi Li, Can you try the following patch and see if it solves your problem. diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c index c269817..184a10a 100644 --- a/arch/powerpc/mm/pkeys.c +++ b/arch/powerpc/mm/pkeys.c @@ -421,7 +421,7 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, * The requested protection is execute-only. Hence let's use an * execute-only pkey. */ - if (prot == PROT_EXEC) { + if (prot == PROT_EXEC && pkey_execute_disable_supported) { pkey = execute_only_pkey(vma->vm_mm); if (pkey > 0) return pkey; Thanks RP