From: Peter Zijlstra <peterz@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: kernel-hardening@lists.openwall.com,
Kees Cook <keescook@chromium.org>,
Greg KH <gregkh@linuxfoundation.org>,
Will Deacon <will.deacon@arm.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Arnd Bergmann <arnd@arndb.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
"H. Peter Anvin" <h.peter.anvin@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [kernel-hardening] Re: [RFC v4 PATCH 00/13] HARDENED_ATOMIC
Date: Sat, 12 Nov 2016 00:07:50 +0100 [thread overview]
Message-ID: <20161111230750.GP3157@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20161111130034.GO3157@twins.programming.kicks-ass.net>
On Fri, Nov 11, 2016 at 02:00:34PM +0100, Peter Zijlstra wrote:
> +static inline bool refcount_sub_and_test(int i, refcount_t *r)
> +{
> + unsigned int old, new, val = atomic_read(&r->refs);
> +
> + for (;;) {
regardless of the sub_and_test vs inc_and_test issue, this should
probably also have:
if (val == UINT_MAX)
return false;
such that we stay saturated. If for some reason someone can trigger more
dec's than inc's, we'd be hosed.
> + new = val - i;
> + if (new > val)
> + BUG(); /* underflow */
> +
> + old = atomic_cmpxchg_release(&r->refs, val, new);
> + if (old == val)
> + break;
> +
> + val = old;
> + }
> +
> + return !new;
> +}
next prev parent reply other threads:[~2016-11-11 23:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1478809488-18303-1-git-send-email-elena.reshetova@intel.com>
2016-11-10 20:37 ` Peter Zijlstra
2016-11-10 20:48 ` Will Deacon
2016-11-10 21:01 ` Kees Cook
2016-11-10 21:23 ` [kernel-hardening] " David Windsor
2016-11-10 21:27 ` Kees Cook
2016-11-10 21:39 ` David Windsor
2016-11-10 21:39 ` Peter Zijlstra
2016-11-10 21:13 ` Peter Zijlstra
2016-11-10 21:23 ` Kees Cook
2016-11-11 4:25 ` [kernel-hardening] " Rik van Riel
2016-11-10 22:27 ` Greg KH
2016-11-10 23:15 ` Kees Cook
2016-11-10 23:38 ` Greg KH
2016-11-10 23:57 ` Peter Zijlstra
2016-11-11 0:29 ` Colin Vidal
2016-11-11 12:41 ` Mark Rutland
2016-11-11 12:47 ` Peter Zijlstra
2016-11-11 13:00 ` Peter Zijlstra
2016-11-11 14:39 ` Thomas Gleixner
2016-11-11 14:48 ` Peter Zijlstra
2016-11-11 23:07 ` Peter Zijlstra [this message]
2016-11-13 11:03 ` Greg KH
2016-11-10 20:56 ` Kees Cook
2016-11-11 3:20 ` [kernel-hardening] " David Windsor
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