linux-kernel - Re: [PATCH v4 00/10] Function Granular KASLR

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Message-ID: <fc6d2289-af97-5cf8-a4bb-77c2b0b8375c@redhat.com>
Date:   Mon, 3 Aug 2020 14:17:41 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     Kees Cook <keescook@...omium.org>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>
Cc:     Kristen Carlson Accardi <kristen@...ux.intel.com>,
        Miroslav Benes <mbenes@...e.cz>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, arjan@...ux.intel.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com, rick.p.edgecombe@...el.com,
        live-patching@...r.kernel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jessica Yu <jeyu@...nel.org>,
        "Frank Ch. Eigler" <fche@...hat.com>
Subject: Re: [PATCH v4 00/10] Function Granular KASLR

On 8/3/20 1:45 PM, Kees Cook wrote:
> On Mon, Aug 03, 2020 at 02:39:32PM +0300, Evgenii Shatokhin wrote:
>> There are at least 2 places where high-order memory allocations might happen
>> during module loading. Such allocations may fail if memory is fragmented,
>> while physically contiguous memory areas are not really needed there. I
>> suggest to switch to kvmalloc/kvfree there.
> 
> While this does seem to be the right solution for the extant problem, I
> do want to take a moment and ask if the function sections need to be
> exposed at all? What tools use this information, and do they just want
> to see the bounds of the code region? (i.e. the start/end of all the
> .text* sections) Perhaps .text.* could be excluded from the sysfs
> section list?
> 

[[cc += FChE, see [0] for Evgenii's full mail ]]

It looks like debugging tools like systemtap [1], gdb [2] and its 
add-symbol-file cmd, etc. peek at the /sys/module/<MOD>/section/ info.

But yeah, it would be preferable if we didn't export a long sysfs 
representation if nobody actually needs it.


[0] 
https://lore.kernel.org/lkml/e9c4d88b-86db-47e9-4299-3fac45a7e3fd@virtuozzo.com/
[1] https://fossies.org/linux/systemtap/staprun/staprun.c
[2] 
https://www.oreilly.com/library/view/linux-device-drivers/0596005903/ch04.html#linuxdrive3-CHP-4-SECT-6.1

-- Joe