lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <6e402f94fe1e942116aca729f1d54fd1399cb98a.camel@intel.com>
Date:   Tue, 15 Nov 2022 20:40:19 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "peterz@...radead.org" <peterz@...radead.org>
CC:     "bsingharora@...il.com" <bsingharora@...il.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "Syromiatnikov, Eugene" <esyr@...hat.com>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "Yu, Yu-cheng" <yu-cheng.yu@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Eranian, Stephane" <eranian@...gle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "fweimer@...hat.com" <fweimer@...hat.com>,
        "nadav.amit@...il.com" <nadav.amit@...il.com>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "dethoma@...rosoft.com" <dethoma@...rosoft.com>,
        "kcc@...gle.com" <kcc@...gle.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "bp@...en8.de" <bp@...en8.de>, "oleg@...hat.com" <oleg@...hat.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "pavel@....cz" <pavel@....cz>, "arnd@...db.de" <arnd@...db.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>,
        "john.allen@....com" <john.allen@....com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "gorcunov@...il.com" <gorcunov@...il.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 18/37] mm: Add guard pages around a shadow stack.

On Tue, 2022-11-15 at 13:04 +0100, Peter Zijlstra wrote:
> On Fri, Nov 04, 2022 at 03:35:45PM -0700, Rick Edgecombe wrote:
> 
> > diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
> > index c90c20904a60..66da1f3298b0 100644
> > --- a/arch/x86/mm/mmap.c
> > +++ b/arch/x86/mm/mmap.c
> > @@ -248,3 +248,26 @@ bool pfn_modify_allowed(unsigned long pfn,
> > pgprot_t prot)
> >                return false;
> >        return true;
> >   }
> > +
> > +unsigned long stack_guard_start_gap(struct vm_area_struct *vma)
> > +{
> > +     if (vma->vm_flags & VM_GROWSDOWN)
> > +             return stack_guard_gap;
> > +
> > +     /*
> > +      * Shadow stack pointer is moved by CALL, RET, and
> > INCSSP(Q/D).
> 
> Can we perhaps write this like: INCSPP[QD] ? The () notation makes it
> look like a function.

Sure.

> 
> > +      * INCSSPQ moves shadow stack pointer up to 255 * 8 = ~2 KB
> > +      * (~1KB for INCSSPD) and touches the first and the last
> > element
> > +      * in the range, which triggers a page fault if the range is
> > not
> > +      * in a shadow stack. Because of this, creating 4-KB guard
> > pages
> > +      * around a shadow stack prevents these instructions from
> > going
> > +      * beyond.
> > +      *
> > +      * Creation of VM_SHADOW_STACK is tightly controlled, so a
> > vma
> > +      * can't be both VM_GROWSDOWN and VM_SHADOW_STACK
> > +      */
> > +     if (vma->vm_flags & VM_SHADOW_STACK)
> > +             return PAGE_SIZE;
> > +
> > +     return 0;
> > +}
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 5d9536fa860a..0a3f7e2b32df 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2832,15 +2832,16 @@ struct vm_area_struct *vma_lookup(struct
> > mm_struct *mm, unsigned long addr)
> >        return mtree_load(&mm->mm_mt, addr);
> >   }
> >   
> > +unsigned long stack_guard_start_gap(struct vm_area_struct *vma);
> > +
> >   static inline unsigned long vm_start_gap(struct vm_area_struct
> > *vma)
> >   {
> > +     unsigned long gap = stack_guard_start_gap(vma);
> >        unsigned long vm_start = vma->vm_start;
> >   
> > -     if (vma->vm_flags & VM_GROWSDOWN) {
> > -             vm_start -= stack_guard_gap;
> > -             if (vm_start > vma->vm_start)
> > -                     vm_start = 0;
> > -     }
> > +     vm_start -= gap;
> > +     if (vm_start > vma->vm_start)
> > +             vm_start = 0;
> >        return vm_start;
> >   }
> >   
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 2def55555e05..f67606fbc464 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -281,6 +281,13 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
> >        return origbrk;
> >   }
> >   
> > +unsigned long __weak stack_guard_start_gap(struct vm_area_struct
> > *vma)
> > +{
> > +     if (vma->vm_flags & VM_GROWSDOWN)
> > +             return stack_guard_gap;
> > +     return 0;
> > +}
> 
> I'm thinking perhaps this wants to be an inline function?

I don't think it can work with weak then.

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ