From: Igor Stoppa <igor.stoppa@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
Kees Cook <keescook@chromium.org>,
igor.stoppa@huawei.com, Nadav Amit <nadav.amit@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-integrity@vger.kernel.org,
kernel-hardening@lists.openwall.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/6] __wr_after_init: write rare for static allocation
Date: Mon, 10 Dec 2018 00:22:56 +0200 [thread overview]
Message-ID: <8959c79b-dd9d-8b1f-87b6-e2c971aa2342@gmail.com> (raw)
In-Reply-To: <20181206044413.GB24603@bombadil.infradead.org>
On 06/12/2018 06:44, Matthew Wilcox wrote:
> On Tue, Dec 04, 2018 at 02:18:01PM +0200, Igor Stoppa wrote:
>> +void *__wr_op(unsigned long dst, unsigned long src, __kernel_size_t len,
>> + enum wr_op_type op)
>> +{
>> + temporary_mm_state_t prev;
>> + unsigned long flags;
>> + unsigned long offset;
>> + unsigned long wr_poking_addr;
>> +
>> + /* Confirm that the writable mapping exists. */
>> + BUG_ON(!wr_ready);
>> +
>> + if (WARN_ONCE(op >= WR_OPS_NUMBER, "Invalid WR operation.") ||
>> + WARN_ONCE(!is_wr_after_init(dst, len), "Invalid WR range."))
>> + return (void *)dst;
>> +
>> + offset = dst - (unsigned long)&__start_wr_after_init;
>> + wr_poking_addr = wr_poking_base + offset;
>> + local_irq_save(flags);
>
> Why not local_irq_disable()? Do we have a use-case for wanting to access
> this from interrupt context?
No, not that I can think of. It was "just in case", but I can remove it.
>> + /* XXX make the verification optional? */
>
> Well, yes. It seems like debug code to me.
Ok, I was not sure about this, because text_poke() does it as part of
its normal operations.
>> + /* Randomize the poking address base*/
>> + wr_poking_base = TASK_UNMAPPED_BASE +
>> + (kaslr_get_random_long("Write Rare Poking") & PAGE_MASK) %
>> + (TASK_SIZE - (TASK_UNMAPPED_BASE + wr_range));
>
> I don't think this is a great idea. We want to use the same mm for both
> static and dynamic wr memory, yes? So we should have enough space for
> all of ram, not splatter the static section all over the address space.
>
> On x86-64 (4 level page tables), we have a 64TB space for all of physmem
> and 128TB of user space, so we can place the base anywhere in a 64TB
> range.
I was actually wondering about the dynamic part.
It's still not clear to me if it's possible to write the code in a
sufficiently generic way that it could work on all 64 bit architectures.
I'll start with x86-64 as you suggest.
--
igor
next prev parent reply other threads:[~2018-12-09 22:24 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-04 12:17 [RFC v1 PATCH 0/6] hardening: statically allocated protected memory Igor Stoppa
2018-12-04 12:18 ` [PATCH 1/6] __wr_after_init: linker section and label Igor Stoppa
2018-12-04 12:18 ` [PATCH 2/6] __wr_after_init: write rare for static allocation Igor Stoppa
2018-12-05 23:13 ` Andy Lutomirski
2018-12-06 9:44 ` Peter Zijlstra
2018-12-09 22:32 ` Igor Stoppa
2018-12-10 9:59 ` Peter Zijlstra
2018-12-09 22:09 ` Igor Stoppa
2018-12-12 9:49 ` Martin Schwidefsky
2018-12-19 22:50 ` Igor Stoppa
2018-12-06 4:44 ` Matthew Wilcox
2018-12-09 22:22 ` Igor Stoppa [this message]
2018-12-04 12:18 ` [PATCH 3/6] rodata_test: refactor tests Igor Stoppa
2018-12-04 12:18 ` [PATCH 4/6] rodata_test: add verification for __wr_after_init Igor Stoppa
2018-12-04 12:18 ` [PATCH 5/6] __wr_after_init: test write rare functionality Igor Stoppa
2018-12-04 12:18 ` [PATCH 6/6] __wr_after_init: lkdtm test Igor Stoppa
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