From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ve0-f171.google.com (mail-ve0-f171.google.com [209.85.128.171]) by kanga.kvack.org (Postfix) with ESMTP id 412AB6B0036 for ; Thu, 15 May 2014 15:59:25 -0400 (EDT) Received: by mail-ve0-f171.google.com with SMTP id oz11so1946763veb.16 for ; Thu, 15 May 2014 12:59:25 -0700 (PDT) Received: from mail-vc0-f172.google.com (mail-vc0-f172.google.com [209.85.220.172]) by mx.google.com with ESMTPS id rl1si1117385vcb.74.2014.05.15.12.59.24 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 15 May 2014 12:59:24 -0700 (PDT) Received: by mail-vc0-f172.google.com with SMTP id hr9so5109655vcb.3 for ; Thu, 15 May 2014 12:59:24 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20140515195320.GR28328@moon> References: <20140514132312.573e5d3cf99276c3f0b82980@linux-foundation.org> <5373D509.7090207@oracle.com> <20140514140305.7683c1c2f1e4fb0a63085a2a@linux-foundation.org> <5373DBE4.6030907@oracle.com> <20140514143124.52c598a2ba8e2539ee76558c@linux-foundation.org> <20140514221140.GF28328@moon> <20140515084558.GI28328@moon> <20140515195320.GR28328@moon> From: Andy Lutomirski Date: Thu, 15 May 2014 12:59:04 -0700 Message-ID: Subject: Re: mm: NULL ptr deref handling mmaping of special mappings Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Cyrill Gorcunov Cc: Andrew Morton , Sasha Levin , "linux-mm@kvack.org" , Dave Jones , LKML , Pavel Emelyanov On Thu, May 15, 2014 at 12:53 PM, Cyrill Gorcunov wrote: > On Thu, May 15, 2014 at 12:46:34PM -0700, Andy Lutomirski wrote: >> On Thu, May 15, 2014 at 1:45 AM, Cyrill Gorcunov wrote: >> > On Wed, May 14, 2014 at 03:23:27PM -0700, Andy Lutomirski wrote: >> >> I can summarize: >> >> >> >> On 3.14 and before, the vdso is just a bunch of ELF headers and >> >> executable data. When executed by 64-bit binaries, it reads from the >> >> fixmap to do its thing. That is, it reads from kernel addresses that >> >> don't have vmas. When executed by 32-bit binaries, it doesn't read >> >> anything, since there was no 32-bit timing code. >> >> >> >> On 3.15, the x86_64 vdso is unchanged. The 32-bit vdso is preceded by >> >> a separate vma containing two pages worth of time-varying read-only >> >> data. The vdso reads those pages using PIC references. >> > >> > Andy, could you please point me where is the code which creates a second vma? >> > latest 3.15 master branch >> >> Search for _install_special_mapping in arch/x86/vdso. It's in a >> different place in 3.15-rc and -next. > > As far as I see _install_special_mapping allocates one vma from cache and > > vma->vm_start = addr; > vma->vm_end = addr + len; > > so where is the second one? Look at its callers in vdso32-setup.c and/or vma.c, depending on version. > >> >> > >> > [root@fc ~]# cat /proc/self/maps >> > ... >> > 7fff57b6e000-7fff57b8f000 rw-p 00000000 00:00 0 [stack] >> > 7fff57bff000-7fff57c00000 r-xp 00000000 00:00 0 [vdso] >> > ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall] >> > [root@fc ~]# >> > >> >> What version and bitness is this? > > x86-64, 3.15-rc5 Aha. Give tip/x86/vdso or -next a try or boot a 32-bit 3.15-rc kernel and you'll see it. --Andy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org