linux-kernel - Re: [PATCH v24 14/30] x86/mm: Shadow Stack page fault error checking

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]

Date:   Fri, 9 Apr 2021 18:12:24 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v24 14/30] x86/mm: Shadow Stack page fault error checking

On Thu, Apr 01, 2021 at 03:10:48PM -0700, Yu-cheng Yu wrote:
> Shadow stack accesses are those that are performed by the CPU where it
> expects to encounter a shadow stack mapping.  These accesses are performed
> implicitly by CALL/RET at the site of the shadow stack pointer.  These
> accesses are made explicitly by shadow stack management instructions like
> WRUSSQ.
> 
> Shadow stacks accesses to shadow-stack mapping can see faults in normal,
> valid operation just like regular accesses to regular mappings.  Shadow
> stacks need some of the same features like delayed allocation, swap and
> copy-on-write.
> 
> Shadow stack accesses can also result in errors, such as when a shadow
> stack overflows, or if a shadow stack access occurs to a non-shadow-stack
> mapping.
> 
> In handling a shadow stack page fault, verify it occurs within a shadow
> stack mapping.  It is always an error otherwise.  For valid shadow stack
> accesses, set FAULT_FLAG_WRITE to effect copy-on-write.  Because clearing
> _PAGE_DIRTY (vs. _PAGE_RW) is used to trigger the fault, shadow stack read
> fault and shadow stack write fault are not differentiated and both are
> handled as a write access.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
 Kirill A. Shutemov