linux-kernel - Re: [PATCH 1/2] kallsyms: add kallsyms_show

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Date:   Wed, 11 May 2022 15:32:29 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Maninder Singh <maninder1.s@...sung.com>
Cc:     mcgrof@...nel.org, avimalin@...il.com, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, kafai@...com,
        songliubraving@...com, yhs@...com, john.fastabend@...il.com,
        kpsingh@...nel.org, pmladek@...e.com, rostedt@...dmis.org,
        senozhatsky@...omium.org, andriy.shevchenko@...ux.intel.com,
        naveen.n.rao@...ux.ibm.com, davem@...emloft.net,
        mhiramat@...nel.org, anil.s.keshavamurthy@...el.com,
        linux@...musvillemoes.dk, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        v.narang@...sung.com, Onkarnath <onkarnath.1@...sung.com>
Subject: Re: [PATCH 1/2] kallsyms: add kallsyms_show_value definition in all
 cases

On Wed, May 11, 2022 at 01:36:56PM +0530, Maninder Singh wrote:
> kallsyms_show_value return false if KALLSYMS is disabled,
> but its usage is done by module.c also.
> Thus when KALLSYMS is disabled, system will not print module
> load address:

Eek, I hadn't see the other changes this depends on. I think those
changes need to be reworked first. Notably in the other patch, this is
no good:

        /* address belongs to module */
        if (add_offset)
                len = sprintf(buf, "0x%p+0x%lx", base, offset);
        else
                len = sprintf(buf, "0x%lx", value);

This is printing raw kernel addresses with no hashing, as far as I can
tell. That's not okay at all.

Once that other patch gets fixed, this one then can be revisited.

And just on naming: "kallsyms_tiny" is a weird name: it's just "ksyms"
-- there's no "all".  :)

-- 
Kees Cook