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Date:   Tue, 18 Jul 2023 18:41:27 +0300
Message-Id: <CU5EUJDXM616.SQKBEGB2RLHL@suppilovahvero>
Cc:     <dave.hansen@linux.intel.com>, <linux-kernel@vger.kernel.org>,
        <linux-sgx@vger.kernel.org>, <cgroups@vger.kernel.org>,
        "Zefan Li" <lizefan.x@bytedance.com>,
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        <kai.huang@intel.com>, <reinette.chatre@intel.com>,
        <zhiquan1.li@intel.com>, <kristen@linux.intel.com>
Subject: Re: [PATCH] cgroup/misc: Fix an overflow
From:   "Jarkko Sakkinen" <jarkko@kernel.org>
To:     "Tejun Heo" <tj@kernel.org>,
        "Haitao Huang" <haitao.huang@linux.intel.com>
References: <20230717184719.85523-1-haitao.huang@linux.intel.com>
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In-Reply-To: <ZLWmdBfcuPUBtk1K@slm.duckdns.org>
Precedence: bulk

On Mon Jul 17, 2023 at 11:37 PM EEST, Tejun Heo wrote:
> Hello,
>
> On Mon, Jul 17, 2023 at 03:19:38PM -0500, Haitao Huang wrote:
> > Actually, we are using atomic_long_t for 'current' which is the same wi=
dth
> > as long defined by arch/compiler. So new_usage should be long to be
> > consistent?
>
> We can use atomic64_t, right? It's slower on 32bit machines but I think i=
t'd
> be better to guarantee resource counter range than micro-optimizing charg=
e
> operations. None of the current users are hot enough for this to matter a=
nd
> if somebody becomes that hot, the difference between atomic_t and atomic6=
4_t
> isn't gonna matter that much. We'd need to batch allocations per-cpu and =
so
> on.

In our context, the microcode of SGX could support 32-bit but by design
we only support 64-bit. So at least with the current implementation this
would not be an issue for SGX.

BR, Jarkko