From: Kees Cook <keescook@chromium.org>
To: Akira Kawata <akirakawata1@gmail.com>
Cc: akpm@linux-foundation.org, adobriyan@gmail.com,
viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
lukas.bulwahn@gmail.com, kernel test robot <lkp@intel.com>,
Eric Biederman <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/2] fs/binfmt_elf: Fix AT_PHDR for unusual ELF files
Date: Thu, 27 Jan 2022 08:23:51 -0800 [thread overview]
Message-ID: <202201270816.5030A2A4B5@keescook> (raw)
In-Reply-To: <20220127125643.cifk2ihnbnxo5wcl@gmail.com>
On Thu, Jan 27, 2022 at 09:56:43PM +0900, Akira Kawata wrote:
> On Wed, Jan 26, 2022 at 09:01:30PM -0800, Kees Cook wrote:
> > [...]
> > 1) The ELF spec says e_phoff is 0 if there's no program header table.
> >
> > The old code would just pass the load_addr as a result. This patch will
> > now retain the same result (phdr_addr defaults to 0). I wonder if there
> > is a bug in this behavior, though? (To be addressed in a different patch
> > if needed...)
> >
>
> It is better to return NULL from load_elf_phdrs when e_phoff == 0, I
> think.
Yeah, right now it just returns a pointer to file offset 0.
I also wonder if we should sanity-check e_phoff vs PT_PHDR? Right now
Linux ignores PT_PHDR. Should we reject loading when e_phoff != PT_PHDR
file offset? (And I wonder if there are "broken" binaries right now that
have bad PT_PHDR segments that have gone unnoticed...)
And now I'm thinking about the excellent ELF loading analysis at:
https://nathanotterness.com/2021/10/tiny_elf_modernized.html
;)
--
Kees Cook
next prev parent reply other threads:[~2022-01-27 16:23 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-12 23:24 [PATCH v4 0/2] [PATCH v4 0/2] fs/binfmt_elf: Fix AT_PHDR for unusual ELF files Akira Kawata
2021-12-12 23:24 ` [PATCH v4 1/2] " Akira Kawata
2022-01-27 5:01 ` Kees Cook
2022-01-27 12:56 ` Akira Kawata
2022-01-27 16:23 ` Kees Cook [this message]
2022-01-28 11:10 ` Akira Kawata
2022-01-28 19:56 ` Kees Cook
2021-12-12 23:24 ` [PATCH v4 2/2] fs/binfmt_elf: Refactor load_elf_binary function Akira Kawata
2022-01-27 5:11 ` Kees Cook
2021-12-12 23:24 ` [PATCH v4 0/2] [PATCH v4 0/2] fs/binfmt_elf: Fix AT_PHDR for unusual ELF files Akira Kawata
2021-12-12 23:35 ` Akira Kawata
2021-12-12 23:24 ` [PATCH v4 1/2] " Akira Kawata
2021-12-12 23:24 ` [PATCH v4 2/2] fs/binfmt_elf: Refactor load_elf_binary function Akira Kawata
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