linux-kernel - Re: What exactly do 32-bit x86 exceptions push on the stack in the CS slot?

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Message-ID: <CA+55aFzCGJD50mkKwsgqWtGJ-NN_sB9GCvxDFY3ZpEoz_oEeiQ@mail.gmail.com>
Date:   Mon, 21 Nov 2016 14:25:34 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Anvin <hpa@...or.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Brian Gerst <brgerst@...il.com>,
        Andy Lutomirski <luto@...nel.org>, tedheadster@...il.com,
        George Spelvin <linux@...izon.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>
Subject: Re: What exactly do 32-bit x86 exceptions push on the stack in the CS slot?

On Mon, Nov 21, 2016 at 2:17 PM,  <hpa@...or.com> wrote:
>
> Now, segment loads have always ignored the top 32 bits; it's an issue when examined by other kinds of code.

Yes. Particularly ptrace and signal information copying. Need to make
sure those things don't look at (or expose) high bits that may be
stale stack contents etc.

               Linus