linux-kernel - Re: [PATCH 3/5] module: Do not expose section addresses to non-CAP

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Date:   Wed, 8 Jul 2020 18:12:33 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Dominik Czarnota <dominik.czarnota@...ilofbits.com>,
        stable@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        KP Singh <kpsingh@...omium.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Will Deacon <will@...nel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Matteo Croce <mcroce@...hat.com>,
        Edward Cree <ecree@...arflare.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Alexander Lobakin <alobakin@...nk.ru>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Ingo Molnar <mingo@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] module: Do not expose section addresses to
 non-CAP_SYSLOG

+++ Kees Cook [02/07/20 16:26 -0700]:
>The printing of section addresses in /sys/module/*/sections/* was not
>using the correct credentials to evaluate visibility.
>
>Before:
>
> # cat /sys/module/*/sections/.*text
> 0xffffffffc0458000
> ...
> # capsh --drop=CAP_SYSLOG -- -c "cat /sys/module/*/sections/.*text"
> 0xffffffffc0458000
> ...
>
>After:
>
> # cat /sys/module/*/sections/*.text
> 0xffffffffc0458000
> ...
> # capsh --drop=CAP_SYSLOG -- -c "cat /sys/module/*/sections/.*text"
> 0x0000000000000000
> ...
>
>Additionally replaces the existing (safe) /proc/modules check with
>file->f_cred for consistency.
>
>Cc: stable@...r.kernel.org
>Reported-by: Dominik Czarnota <dominik.czarnota@...ilofbits.com>
>Fixes: be71eda5383f ("module: Fix display of wrong module .text address")
>Signed-off-by: Kees Cook <keescook@...omium.org>

Tested-by: Jessica Yu <jeyu@...nel.org>
Acked-by: Jessica Yu <jeyu@...nel.org>