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Date: Thu, 8 Feb 2018 11:00:18 -0800
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC] x86: KASAN: Sanitize unauthorized irq stack access
Message-ID: <20180208190016.GC9524@bombadil.infradead.org>
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To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>, Kirill Tkhai <ktkhai@virtuozzo.com>, Dave Hansen <dave.hansen@linux.intel.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Alexander Potapenko <glider@google.com>, Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>, Juergen Gross <jgross@suse.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Kees Cook <keescook@chromium.org>, Mathias Krause <minipli@googlemail.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Kate Stewart <kstewart@linuxfoundation.org>, LKML <linux-kernel@vger.kernel.org>, kasan-dev <kasan-dev@googlegroups.com>, Linux-MM <linux-mm@kvack.org>

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.

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