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Subject: Re: [PATCH v2 7/8] exec: Generic execfd support
To:     "Eric W. Biederman" <ebiederm@xmission.com>,
        linux-kernel@vger.kernel.org
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
        Kees Cook <keescook@chromium.org>,
        Greg Ungerer <gerg@linux-m68k.org>,
        Bernd Edlinger <bernd.edlinger@hotmail.de>,
        linux-fsdevel@vger.kernel.org, Al Viro <viro@ZenIV.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Casey Schaufler <casey@schaufler-ca.com>,
        linux-security-module@vger.kernel.org,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Andy Lutomirski <luto@amacapital.net>
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From:   Rob Landley <rob@landley.net>
Message-ID: <adaced72-d757-e3e4-cfeb-5512533d0aa5@landley.net>
Date:   Tue, 19 May 2020 16:59:06 -0500
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On 5/18/20 7:33 PM, Eric W. Biederman wrote:
> 
> Most of the support for passing the file descriptor of an executable
> to an interpreter already lives in the generic code and in binfmt_elf.
> Rework the fields in binfmt_elf that deal with executable file
> descriptor passing to make executable file descriptor passing a first
> class concept.

I was reading this to try to figure out how to do execve(NULL, argv[], envp) to
re-exec self after a vfork() in a chroot with no /proc, and hit the most trivial
quibble ever:

> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1323,7 +1323,10 @@ int begin_new_exec(struct linux_binprm * bprm)
>  	 */
>  	set_mm_exe_file(bprm->mm, bprm->file);
>  
> +	/* If the binary is not readable than enforce mm->dumpable=0 */

then

Rob