Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 8 Jan 2021 19:09:35 +0100
From:   Borislav Petkov <bp@suse.de>
To:     "Chang S. Bae" <chang.seok.bae@intel.com>
Cc:     tglx@linutronix.de, mingo@kernel.org, luto@kernel.org,
        x86@kernel.org, len.brown@intel.com, dave.hansen@intel.com,
        hjl.tools@gmail.com, Dave.Martin@arm.com, jannh@google.com,
        mpe@ellerman.id.au, tony.luck@intel.com, ravi.v.shankar@intel.com,
        libc-alpha@sourceware.org, linux-arch@vger.kernel.org,
        linux-api@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/4] x86/signal: Prevent an alternate stack overflow
 before a signal delivery
Message-ID: <20210108180935.GB12995@zn.tnic>
References: <20201223015312.4882-1-chang.seok.bae@intel.com>
 <20201223015312.4882-4-chang.seok.bae@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20201223015312.4882-4-chang.seok.bae@intel.com>
Precedence: bulk

On Tue, Dec 22, 2020 at 05:53:11PM -0800, Chang S. Bae wrote:
> The kernel pushes data on the userspace stack when entering a signal. If
> using a sigaltstack(), the kernel precisely knows the user stack size.
^^^^^^^^^^^^^^^^^^^^^^^

Formulate properly.

> 
> When the kernel knows that the user stack is too small, avoid the overflow
> and do an immediate SIGSEGV instead.
      ^^^^^^^^^^^^^^^^^^^^^^^

Ditto.

> This overflow is known to occur on systems with large XSAVE state. The
> effort to increase the size typically used for altstacks reduces the
						^^^^^^^^^^

"alternate signal stacks"

-- 
Regards/Gruss,
    Boris.

SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg