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Re: [PATCH v2 0/2] x86, refcount: Implement fast refcount overflow

From "PaX Team" <pageexec@freemail.hu>
Newsgroups linux.kernel
Subject Re: [PATCH v2 0/2] x86, refcount: Implement fast refcount overflow
Date 2017-04-26 04:10 +0200
Message-ID <tAkyZ-4lo-3@gated-at.bofh.it> (permalink)
References <tAhB7-2jd-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 25 Apr 2017 at 15:56, Kees Cook wrote:

> This protection is a modified version of the x86 PAX_REFCOUNT
> implementation from PaX/grsecurity. This speeds up the refcount_t API by
> duplicating the existing atomic_t implementation with a single instruction
> added to detect if the refcount has wrapped past INT_MAX (or below 0)
> resulting in a signed value.

'signed value' sounds somewhat ambiguous given that in C a signed type (such
as the one beneath refcount_t) can have both negative and positive values yet
you didn't mean the latter here i guess.

> Various differences from PaX:
> - uses "js" instead of "jo" to trap all signed results instead of just
>   under/overflow transitions

there're differences in my 4.11 port but this isn't one of them.

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Thread

[PATCH v2 0/2] x86, refcount: Implement fast refcount overflow Kees Cook <keescook@chromium.org> - 2017-04-26 01:00 +0200
  Re: [PATCH v2 0/2] x86, refcount: Implement fast refcount overflow "PaX Team" <pageexec@freemail.hu> - 2017-04-26 04:10 +0200
    Re: [PATCH v2 0/2] x86, refcount: Implement fast refcount overflow Kees Cook <keescook@chromium.org> - 2017-04-26 06:00 +0200

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