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Date:   Sun, 6 Aug 2023 18:23:46 +0200
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To:     Eric Biederman <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: binfmt_misc & different PE binaries
Message-ID: <20230806162346.v7gjoev2nepxlcox@pali>
References: <20230706115550.sqyh3k26e2glz2lu@pali>
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Hello, I would like to remind this email about binfmt_misc for PE.

On Thursday 06 July 2023 13:55:50 Pali Rohár wrote:
> Hello,
> 
> I would like to ask how to properly register binfmt_misc for different
> PE binaries, so kernel could execute the correct loader for them.
> 
> I mean, how to register support for Win32 (console/gui) PE binaries and
> also for CLR PE binaries (dotnet). Win32 needs to be executed under wine
> and CLR ideally under dotnet core (or mono).
> 
> I have read kernel documentation files admin-guide/binfmt-misc.rst
> and admin-guide/mono.rst. But seems that they are in conflicts as both
> wants to registers its own handler for the same magic:
> 
>   echo ':DOSWin:M::MZ::/usr/local/bin/wine:' > register
> 
>   echo ':CLR:M::MZ::/usr/bin/mono:' > /proc/sys/fs/binfmt_misc/register
> 
> Not mentioning the fact that they register DOS MZ handler, which matches
> not only all PE binaries (including EFI, libraries, other processors),
> but also all kind of other NE/LE/LX binaries and different DOS extenders.
> 
> From documentation it looks like that even registering PE binaries is
> impossible by binfmt_misc as PE is detected by checking that indirect
> reference from 0x3C is PE\0\0. And distinguish between Win32 and CLR
> needs to parse PE COM descriptor directory.
> 
> Or it is possible to write binfmt_misc pattern match based on indirect
> offset?