linux-kernel - Re: [PATCH] mm: Fix int overflow in callers of do_shrink

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Date:   Fri, 28 Sep 2018 07:35:48 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     akpm@...ux-foundation.org, gorcunov@...nvz.org, mhocko@...e.com,
        aryabinin@...tuozzo.com, hannes@...xchg.org,
        penguin-kernel@...ove.SAKURA.ne.jp, shakeelb@...gle.com,
        jbacik@...com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: Fix int overflow in callers of do_shrink_slab()

On Fri, Sep 28, 2018 at 02:28:32PM +0300, Kirill Tkhai wrote:
> do_shrink_slab() returns unsigned long value, and
> the placing into int variable cuts high bytes off.
> Then we compare ret and 0xfffffffe (since SHRINK_EMPTY
> is converted to ret type).
> 
> Thus, big number of objects returned by do_shrink_slab()
> may be interpreted as SHRINK_EMPTY, if low bytes of
> their value are equal to 0xfffffffe. Fix that
> by declaration ret as unsigned long in these functions.
> 
> Reported-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>

Reviewed-by: Josef Bacik <josef@...icpanda.com>

Thanks,

Josef