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In-Reply-To: <20211211173447.4155374-1-hjl.tools@gmail.com>
References: <20211211173447.4155374-1-hjl.tools@gmail.com>
From:   Alexey Dobriyan <adobriyan@gmail.com>
Date:   Sun, 12 Dec 2021 09:38:54 +0200
Message-ID: <CACVxJT-k664=aYp4VkG1LH3PsGHEf50PqP5EA+JWiFVb_JVs2Q@mail.gmail.com>
Subject: Re: [PATCH] fs/binfmt_elf.c: disallow zero entry point address
To:     "H.J. Lu" <hjl.tools@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
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On 12/11/21, H.J. Lu <hjl.tools@gmail.com> wrote:
> According to gABI, the entry point address in the ELF header gives the
> virtual address to which the system first transfers control, thus
> starting the process.  If the file has no associated entry point, this
> member holds zero.  Update the ELF loader to disallow an ELF binary
> with zero entry point address.  This fixes:
>
> https://bugzilla.kernel.org/show_bug.cgi?id=215303
>
> Tested by booting Fedora 35 and running a shared library with zero entry
> point address:
>
> $ readelf -h load.so | grep "Entry point address:"
>   Entry point address:               0x0
> $ ./load.so
> bash: ./load.so: cannot execute binary file: Exec format error

Why not let it segfault?

> +	if (elf_ex->e_entry == 0)
> +		goto out;