linux-kernel - Re: [PATCH 1/5] gcc-plugins/stackleak: Exclude alloca() from the instrumentation logic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 4 Jun 2020 16:01:30 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Alexander Popov <alex.popov@...ux.com>,
        Kees Cook <keescook@...omium.org>,
        Elena Reshetova <elena.reshetova@...el.com>
Cc:     Emese Revfy <re.emese@...il.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Jessica Yu <jeyu@...nel.org>,
        Sven Schnelle <svens@...ckframe.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Collingbourne <pcc@...gle.com>,
        Naohiro Aota <naohiro.aota@....com>,
        Alexander Monakov <amonakov@...ras.ru>,
        Mathias Krause <minipli@...glemail.com>,
        PaX Team <pageexec@...email.hu>,
        Brad Spengler <spender@...ecurity.net>,
        Laura Abbott <labbott@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        linux-kbuild@...r.kernel.org,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        kernel list <linux-kernel@...r.kernel.org>, gcc@....gnu.org,
        notify@...nel.org
Subject: Re: [PATCH 1/5] gcc-plugins/stackleak: Exclude alloca() from the
 instrumentation logic

On Thu, Jun 4, 2020 at 3:51 PM Alexander Popov <alex.popov@...ux.com> wrote:
> Some time ago Variable Length Arrays (VLA) were removed from the kernel.
> The kernel is built with '-Wvla'. Let's exclude alloca() from the
> instrumentation logic and make it simpler. The build-time assertion
> against alloca() is added instead.
[...]
> +                       /* Variable Length Arrays are forbidden in the kernel */
> +                       gcc_assert(!is_alloca(stmt));

There is a patch series from Elena and Kees on the kernel-hardening
list that deliberately uses __builtin_alloca() in the syscall entry
path to randomize the stack pointer per-syscall - see
<https://lore.kernel.org/kernel-hardening/20200406231606.37619-4-keescook@chromium.org/>.