linux-kernel - Re: [PATCH RFC] x86: KASAN: Sanitize unauthorized irq stack access

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Message-ID: <20180208190016.GC9524@bombadil.infradead.org>
Date:   Thu, 8 Feb 2018 11:00:18 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Juergen Gross <jgross@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Mathias Krause <minipli@...glemail.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH RFC] x86: KASAN: Sanitize unauthorized irq stack access

On Thu, Feb 08, 2018 at 11:20:26AM -0600, Josh Poimboeuf wrote:
> The patch description is confusing.  It talks about "crappy drivers irq
> handlers when they access wrong memory on the stack".  But if I
> understand correctly, the patch doesn't actually protect against that
> case, because irq handlers run on the irq stack, and this patch only
> affects code which *isn't* running on the irq stack.

This would catch a crappy driver which allocates some memory on the
irq stack, squirrels the pointer to it away in a data structure, then
returns to process (or softirq) context and dereferences the pointer.

I have no idea if that's the case that Kirill is tracking down, but it's
something I can imagine someone doing.