From: Kees Cook <keescook@chromium.org>
To: Julius Hemanth Pitti <jpitti@cisco.com>,
mingo@elte.hu, akpm@linux-foundation.org
Cc: yzaikin@google.com, mcgrof@kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
viro@zeniv.linux.org.uk, xe-linux-external@cisco.com,
jannh@google.com
Subject: Re: [PATCH] proc/sysctl: make protected_* world readable
Date: Thu, 9 Jul 2020 21:31:37 -0700 [thread overview]
Message-ID: <202007092122.782EE053@keescook> (raw)
In-Reply-To: <20200709235115.56954-1-jpitti@cisco.com>
On Thu, Jul 09, 2020 at 04:51:15PM -0700, Julius Hemanth Pitti wrote:
> protected_* files have 600 permissions which prevents
> non-superuser from reading them.
>
> Container like "AWS greengrass" refuse to launch unless
> protected_hardlinks and protected_symlinks are set. When
> containers like these run with "userns-remap" or "--user"
> mapping container's root to non-superuser on host, they
> fail to run due to denied read access to these files.
>
> As these protections are hardly a secret, and do not
> possess any security risk, making them world readable.
>
> Though above greengrass usecase needs read access to
> only protected_hardlinks and protected_symlinks files,
> setting all other protected_* files to 644 to keep
> consistency.
>
> Fixes: 800179c9b8a1 ("fs: add link restrictions")
> Signed-off-by: Julius Hemanth Pitti <jpitti@cisco.com>
Acked-by: Kees Cook <keescook@chromium.org>
I had originally proposed it as 0644, but Ingo asked that it have
a more conservative default value[1]. I figured that given the settings
can be discovered easily, it's not worth much. And if there are legit
cases where things are improved, I don't have a problem switching this
back.
Ingo, any thoughts on this now, 8 years later in the age of containers?
:)
(One devil's advocate question: as a workaround, you are able to just
change those files to 0644 after mounting /proc, yes? But regardless,
why get in people's way for no justifiable reason.)
-Kees
[1] https://lore.kernel.org/lkml/20120105091704.GB3249@elte.hu/
--
Kees Cook
next prev parent reply other threads:[~2020-07-10 4:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-09 23:51 [PATCH] proc/sysctl: make protected_* world readable Julius Hemanth Pitti
2020-07-10 4:31 ` Kees Cook [this message]
2020-07-29 0:03 ` Luis Chamberlain
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