linux-kernel - Re: [RFC PATCH 01/11] modpost: Support >64K sections

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Message-ID: <202002060438.C2C977F8@keescook>
Date:   Thu, 6 Feb 2020 04:38:52 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Kristen Carlson Accardi <kristen@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        arjan@...ux.intel.com, rick.p.edgecombe@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [RFC PATCH 01/11] modpost: Support >64K sections

On Wed, Feb 05, 2020 at 02:39:40PM -0800, Kristen Carlson Accardi wrote:
> According to the ELF specification, if the value of st_shndx
> contains SH_XINDEX, the actual section header index is too
> large to fit in the st_shndx field and you should use the
> value out of the SHT_SYMTAB_SHNDX section instead. This table
> was already being parsed and saved into symtab_shndx_start, however
> it was not being used, causing segfaults when the number of
> sections is greater than 64K. Check the st_shndx field for
> SHN_XINDEX prior to using.
> 
> Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>

Looking at "readelf" output continues to make me laugh. :)

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

-- 
Kees Cook