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Subject: Re: [PATCH] x86/fpu/xstate: Clear uninitialized xstate areas in
 core dump
From:   Yu-cheng Yu <yu-cheng.yu@intel.com>
To:     Dave Hansen <dave.hansen@intel.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Rik van Riel <riel@surriel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     sam <sunhaoyl@outlook.com>, Kees Cook <keescook@chromium.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Potapenko <glider@google.com>,
        Al Viro <viro@zeniv.linux.org.uk>, stable@vger.kernel.org
Date:   Thu, 07 May 2020 10:12:16 -0700
In-Reply-To: <c26a39cc-1387-b55c-ec45-ec0e2357dd47@intel.com>
References: <20200507164904.26927-1-yu-cheng.yu@intel.com>
         <c26a39cc-1387-b55c-ec45-ec0e2357dd47@intel.com>
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On Thu, 2020-05-07 at 09:52 -0700, Dave Hansen wrote:
> On 5/7/20 9:49 AM, Yu-cheng Yu wrote:
> > In a core dump, copy_xstate_to_kernel() copies only enabled user xfeatures
> > to a kernel buffer without touching areas for disabled xfeatures.  However,
> > those uninitialized areas may contain random data, which is then written to
> > the core dump file and can be read by a non-privileged user.
> > 
> > Fix it by clearing uninitialized areas.
> 
> Do you have a Fixes: tag for this, or some background on where this
> issue originated that might be helpful for backports?

I will add that.