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Thu, 25 Jun 2020 22:40:18 +0000 (UTC) IronPort-SDR: TZCwUHtnMFLVu+2USaglOYMvlXwAxDYCl8+fSBZhTtkF7gi8hFIs5oX5D6EGc/pCE1BSfr07RY rfXoEQ/yfiSw== X-IronPort-AV: E=McAfee;i="6000,8403,9663"; a="145162536" X-IronPort-AV: E=Sophos;i="5.75,280,1589266800"; d="scan'208";a="145162536" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jun 2020 15:40:17 -0700 IronPort-SDR: pcAXwb9yQiL0xZNaBVRyCJV77i34uuWomPinHUgK9MTjbZx8DQ3nVrdWpAFLY2nBC41ls/7Oe4 7GQgSHOdBz2Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,280,1589266800"; d="scan'208";a="385605612" Received: from jproldan-mobl.ger.corp.intel.com (HELO localhost) ([10.252.49.123]) by fmsmga001.fm.intel.com with ESMTP; 25 Jun 2020 15:40:05 -0700 Date: Fri, 26 Jun 2020 01:40:04 +0300 From: Jarkko Sakkinen To: Sean Christopherson Cc: Matthew Wilcox , Borislav Petkov , x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, Jethro Beekman , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com, linux-mm@kvack.org Subject: Re: [PATCH v33 10/21] mm: Introduce vm_ops->may_mprotect() Message-ID: <20200625224004.GA31121@linux.intel.com> References: <20200617220844.57423-1-jarkko.sakkinen@linux.intel.com> <20200617220844.57423-11-jarkko.sakkinen@linux.intel.com> <20200625171416.GI20319@zn.tnic> <20200625173050.GF7703@casper.infradead.org> <20200625180646.GF3437@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200625180646.GF3437@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo X-Rspamd-Queue-Id: 8C21337612 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 25, 2020 at 11:06:46AM -0700, Sean Christopherson wrote: > On Thu, Jun 25, 2020 at 06:30:50PM +0100, Matthew Wilcox wrote: > > On Thu, Jun 25, 2020 at 07:14:16PM +0200, Borislav Petkov wrote: > > > On Thu, Jun 18, 2020 at 01:08:32AM +0300, Jarkko Sakkinen wrote: > > > > diff --git a/mm/mprotect.c b/mm/mprotect.c > > > > index ce8b8a5eacbb..f7731dc13ff0 100644 > > > > --- a/mm/mprotect.c > > > > +++ b/mm/mprotect.c > > > > @@ -603,13 +603,21 @@ static int do_mprotect_pkey(unsigned long start, size_t len, > > > > goto out; > > > > } > > > > > > > > + tmp = vma->vm_end; > > > > + if (tmp > end) > > > > + tmp = end; > > > > + > > > > + if (vma->vm_ops && vma->vm_ops->may_mprotect) { > > > > + error = vma->vm_ops->may_mprotect(vma, nstart, tmp, > > > > + prot); > > > > + if (error) > > > > + goto out; > > > > + } > > > > + > > > > error = security_file_mprotect(vma, reqprot, prot); > > > > if (error) > > > > goto out; > > > > > > > > I think the right way to do this is: > > > > error = security_file_mprotect(vma, reqprot, prot); > > if (error) > > goto out; > > > > tmp = vma->vm_end; > > if (tmp > end) > > tmp = end; > > + if (vma->vm_ops->mprotect) > > + error = vma->vm_ops->mprotect(vma, &prev, nstart, tmp, > > + newflags); > > + else > > + error = mprotect_fixup(vma, &prev, nstart, tmp, > > + newflags); > > - error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); > > if (error) > > goto out; > > > > and then the vma owner can do whatever it needs to before calling > > mprotect_fixup(), which is already not static. > > I'm certainly not opposed to a straight ->mprotect() hook. ->may_protect() > came about because I/we thought it would be less objectionable to allow the > vma owner to apply additional restrictions as opposed to a wholesale > replacement. Can you send fixes to associated patches to linux-sgx (i.e. this and driver)? > > (how did we get to v33 with this kind of problem still in the patch set?) > > Because no one from the mm world has looked at it. Which is completely > understandable because it's a giant patch set and the first 25 or so versions > were spent sorting out fundamental architectural/design issue (there have > been a _lot_ of speed bumps), e.g. the need for hooking mprotect() didn't > even come about until v21. Actually also because we did not have an explicit linux-mm CC. /Jarkko