linux-kernel - Re: [PATCH 3/4] sparc: convert mdesc_handle.refcnt from atomic_t to refcount

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Date:   Mon, 03 Apr 2017 06:12:52 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     elena.reshetova@...el.com
Cc:     linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
        x86@...nel.org, sparclinux@...r.kernel.org,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        peterz@...radead.org, gregkh@...uxfoundation.org,
        tglx@...utronix.de, mingo@...hat.com, tony.luck@...el.com,
        hpa@...or.com, ishkamiel@...il.com, keescook@...omium.org,
        dwindsor@...il.com
Subject: Re: [PATCH 3/4] sparc: convert mdesc_handle.refcnt from atomic_t
 to refcount_t

From: "Reshetova, Elena" <elena.reshetova@...el.com>
Date: Mon, 3 Apr 2017 07:28:01 +0000

> 
>> From: Elena Reshetova <elena.reshetova@...el.com>
>> Date: Mon, 20 Feb 2017 13:06:20 +0200
>> 
>> > refcount_t type and corresponding API should be
>> > used instead of atomic_t when the variable is used as
>> > a reference counter. This allows to avoid accidental
>> > refcounter overflows that might lead to use-after-free
>> > situations.
>> >
>> > Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
>> > Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
>> > Signed-off-by: Kees Cook <keescook@...omium.org>
>> > Signed-off-by: David Windsor <dwindsor@...il.com>
>> 
>> Acked-by: David S. Miller <davem@...emloft.net>
> 
> Hi David, 
> 
> Would you be able to propagate this patch further or should I send
> it (with your acked-by) once more to specific list/maintainer for
> the inclusion?

I'm generally not happy with the refcount_t and the added overhead it
has compared to the existing atomic_t operations.

I know it is going to make a difference for networking.

I understand that this sparc case is a slow path, but I know that if
we just apply all of these refcount_t conversions, there will be no
work done to address the performance issues.

So I'm reluctant to ACK in any way these refcount_t conversions,
sorry.