From: David Windsor <dwindsor-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: Jeff Layton <jlayton-vpEMnDpepFuMZCB2o+C8xQ@public.gmane.org>,
linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
kernel-hardening-ZwoEplunGu1jrUoiu81ncdBPR1lH4CV8@public.gmane.org,
Bruce Fields <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>,
Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
"Reshetova,
Elena" <elena.reshetova-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [RFC][PATCH] nfsd: add +1 to reference counting scheme for struct nfsd4_session
Date: Mon, 13 Feb 2017 06:42:56 -0500 [thread overview]
Message-ID: <CAEXv5_g=DS4wk0mgZuw-doVCqountb-CxZki1LOoQH-P7W1U4A@mail.gmail.com> (raw)
In-Reply-To: <20170213103815.GA5131-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
On Mon, Feb 13, 2017 at 5:38 AM, Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> wrote:
> On Sat, Feb 11, 2017 at 09:01:15AM -0500, David Windsor wrote:
>> I'm not sure there's another way to accomplish what we need
>> (initializing struct nfsd4_session objects with refcount=1) without
>> also modifying the freeable reference state. After migrating to the
>> refcount_t API, if we leave init_session() as is, the first call to
>> nfsd4_get_session_locked() will fail:
>
> Which is a pretty clear indicator that this code should simply not
> migrate to the recount_t API. Why was it even considered if the
> conversion is obviously broken?
I'm not sure this is a sound argument for not converting to
refcount_t. In other locations in which refcounting schemes are
"unnatural," i.e. freeing refcounted objects when their refcount is -1
(rather than 0), conversion to refcount_t is accomplished by
performing a logical +1 to the overall refcounting scheme. We're
auditing all refcounting corner cases, such as these, to see if
similar solutions can be found.
Thanks,
David
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WARNING: multiple messages have this Message-ID (diff)
From: David Windsor <dwindsor@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jeff Layton <jlayton@poochiereds.net>,
linux-nfs@vger.kernel.org, netdev@vger.kernel.org,
kernel-hardening@lists.openwall.com,
Bruce Fields <bfields@fieldses.org>,
Kees Cook <keescook@chromium.org>,
"Reshetova, Elena" <elena.reshetova@intel.com>
Subject: Re: [RFC][PATCH] nfsd: add +1 to reference counting scheme for struct nfsd4_session
Date: Mon, 13 Feb 2017 06:42:56 -0500 [thread overview]
Message-ID: <CAEXv5_g=DS4wk0mgZuw-doVCqountb-CxZki1LOoQH-P7W1U4A@mail.gmail.com> (raw)
In-Reply-To: <20170213103815.GA5131@infradead.org>
On Mon, Feb 13, 2017 at 5:38 AM, Christoph Hellwig <hch@infradead.org> wrote:
> On Sat, Feb 11, 2017 at 09:01:15AM -0500, David Windsor wrote:
>> I'm not sure there's another way to accomplish what we need
>> (initializing struct nfsd4_session objects with refcount=1) without
>> also modifying the freeable reference state. After migrating to the
>> refcount_t API, if we leave init_session() as is, the first call to
>> nfsd4_get_session_locked() will fail:
>
> Which is a pretty clear indicator that this code should simply not
> migrate to the recount_t API. Why was it even considered if the
> conversion is obviously broken?
I'm not sure this is a sound argument for not converting to
refcount_t. In other locations in which refcounting schemes are
"unnatural," i.e. freeing refcounted objects when their refcount is -1
(rather than 0), conversion to refcount_t is accomplished by
performing a logical +1 to the overall refcounting scheme. We're
auditing all refcounting corner cases, such as these, to see if
similar solutions can be found.
Thanks,
David
WARNING: multiple messages have this Message-ID (diff)
From: David Windsor <dwindsor@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jeff Layton <jlayton@poochiereds.net>,
linux-nfs@vger.kernel.org, netdev@vger.kernel.org,
kernel-hardening@lists.openwall.com,
Bruce Fields <bfields@fieldses.org>,
Kees Cook <keescook@chromium.org>,
"Reshetova, Elena" <elena.reshetova@intel.com>
Subject: [kernel-hardening] Re: [RFC][PATCH] nfsd: add +1 to reference counting scheme for struct nfsd4_session
Date: Mon, 13 Feb 2017 06:42:56 -0500 [thread overview]
Message-ID: <CAEXv5_g=DS4wk0mgZuw-doVCqountb-CxZki1LOoQH-P7W1U4A@mail.gmail.com> (raw)
In-Reply-To: <20170213103815.GA5131@infradead.org>
On Mon, Feb 13, 2017 at 5:38 AM, Christoph Hellwig <hch@infradead.org> wrote:
> On Sat, Feb 11, 2017 at 09:01:15AM -0500, David Windsor wrote:
>> I'm not sure there's another way to accomplish what we need
>> (initializing struct nfsd4_session objects with refcount=1) without
>> also modifying the freeable reference state. After migrating to the
>> refcount_t API, if we leave init_session() as is, the first call to
>> nfsd4_get_session_locked() will fail:
>
> Which is a pretty clear indicator that this code should simply not
> migrate to the recount_t API. Why was it even considered if the
> conversion is obviously broken?
I'm not sure this is a sound argument for not converting to
refcount_t. In other locations in which refcounting schemes are
"unnatural," i.e. freeing refcounted objects when their refcount is -1
(rather than 0), conversion to refcount_t is accomplished by
performing a logical +1 to the overall refcounting scheme. We're
auditing all refcounting corner cases, such as these, to see if
similar solutions can be found.
Thanks,
David
next prev parent reply other threads:[~2017-02-13 11:42 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-09 7:38 [RFC][PATCH] nfsd: add +1 to reference counting scheme for struct nfsd4_session David Windsor
2017-02-09 7:38 ` [kernel-hardening] " David Windsor
2017-02-09 7:38 ` David Windsor
2017-02-11 6:42 ` David Windsor
2017-02-11 6:42 ` [kernel-hardening] " David Windsor
[not found] ` <CAEXv5_jUa8Av4JABoKSAueiLHSLzibMvaE-8DrVcxZHFceckMg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-02-11 12:31 ` Jeff Layton
2017-02-11 12:31 ` [kernel-hardening] " Jeff Layton
2017-02-11 12:31 ` Jeff Layton
[not found] ` <1486816302.4233.29.camel-vpEMnDpepFuMZCB2o+C8xQ@public.gmane.org>
2017-02-11 14:01 ` David Windsor
2017-02-11 14:01 ` [kernel-hardening] " David Windsor
2017-02-11 14:01 ` David Windsor
2017-02-11 14:09 ` Jeff Layton
2017-02-11 14:09 ` [kernel-hardening] " Jeff Layton
[not found] ` <CAEXv5_gd7F-eaazzU1BWPzH4huhEcO1Y-FWov5UP9T+6R+fv-A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-02-13 10:38 ` Christoph Hellwig
2017-02-13 10:38 ` [kernel-hardening] " Christoph Hellwig
2017-02-13 10:38 ` Christoph Hellwig
[not found] ` <20170213103815.GA5131-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-02-13 11:42 ` David Windsor [this message]
2017-02-13 11:42 ` [kernel-hardening] " David Windsor
2017-02-13 11:42 ` David Windsor
[not found] ` <CAEXv5_g=DS4wk0mgZuw-doVCqountb-CxZki1LOoQH-P7W1U4A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-02-13 12:12 ` Christoph Hellwig
2017-02-13 12:12 ` [kernel-hardening] " Christoph Hellwig
2017-02-13 12:12 ` Christoph Hellwig
2017-02-14 13:48 ` David Windsor
2017-02-14 13:48 ` [kernel-hardening] " David Windsor
2017-02-12 1:15 ` Bruce Fields
2017-02-12 1:15 ` [kernel-hardening] " Bruce Fields
2017-02-12 1:15 ` Bruce Fields
2017-02-12 1:42 ` David Windsor
2017-02-12 1:42 ` [kernel-hardening] " David Windsor
2017-02-13 10:54 ` Hans Liljestrand
2017-02-13 10:54 ` Hans Liljestrand
2017-02-13 11:46 ` David Windsor
[not found] ` <CAEXv5_hP39k7HSLP-G_khx7MMQHnk=8Z5caa+U5n3bYvUTE1gQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-02-15 16:45 ` Bruce Fields
2017-02-15 16:45 ` Bruce Fields
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