linux-kernel - Re: [PATCH 12/13] x86/jitalloc: prepare to allocate exectuatble memory as ROX

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: <B021EE82-9741-4B41-8FF7-91A9336EDD7C@gmail.com>
Date:   Mon, 5 Jun 2023 14:11:26 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc:     "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "rppt@...nel.org" <rppt@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "deller@....de" <deller@....de>,
        "mcgrof@...nel.org" <mcgrof@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "hca@...ux.ibm.com" <hca@...ux.ibm.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kent.overstreet@...ux.dev" <kent.overstreet@...ux.dev>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "palmer@...belt.com" <palmer@...belt.com>,
        "chenhuacai@...nel.org" <chenhuacai@...nel.org>,
        "tsbogend@...ha.franken.de" <tsbogend@...ha.franken.de>,
        "linux-trace-kernel@...r.kernel.org" 
        <linux-trace-kernel@...r.kernel.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Will Deacon <will@...nel.org>,
        "dinguyen@...nel.org" <dinguyen@...nel.org>,
        "naveen.n.rao@...ux.ibm.com" <naveen.n.rao@...ux.ibm.com>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "song@...nel.org" <song@...nel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "loongarch@...ts.linux.dev" <loongarch@...ts.linux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 12/13] x86/jitalloc: prepare to allocate exectuatble
 memory as ROX



> On Jun 5, 2023, at 9:10 AM, Edgecombe, Rick P <rick.p.edgecombe@...el.com> wrote:
> 
> On Mon, 2023-06-05 at 11:11 +0300, Mike Rapoport wrote:
>> On Sun, Jun 04, 2023 at 10:52:44PM -0400, Steven Rostedt wrote:
>>> On Thu, 1 Jun 2023 16:54:36 -0700
>>> Nadav Amit <nadav.amit@...il.com> wrote:
>>> 
>>>>> The way text_poke() is used here, it is creating a new writable
>>>>> alias
>>>>> and flushing it for *each* write to the module (like for each
>>>>> write of
>>>>> an individual relocation, etc). I was just thinking it might
>>>>> warrant
>>>>> some batching or something.  
>> 
>>>> I am not advocating to do so, but if you want to have many
>>>> efficient
>>>> writes, perhaps you can just disable CR0.WP. Just saying that if
>>>> you
>>>> are about to write all over the memory, text_poke() does not
>>>> provide
>>>> too much security for the poking thread.
>> 
>> Heh, this is definitely and easier hack to implement :)
> 
> I don't know the details, but previously there was some strong dislike
> of CR0.WP toggling. And now there is also the problem of CET. Setting
> CR0.WP=0 will #GP if CR4.CET is 1 (as it currently is for kernel IBT).
> I guess you might get away with toggling them both in some controlled
> situation, but it might be a lot easier to hack up then to be made
> fully acceptable. It does sound much more efficient though.

Thanks for highlighting this issue. I understand the limitations of
CR0.WP. There is also always the concerns that without CET or other
control flow integrity mechanism, someone would abuse (using ROP/JOP)
functions that clear CR0.WP…