linux-kernel - Re: [PATCH] selinux: avc: mark avc node as not a leak

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Message-ID: <20190109113126.nzpmb7xx4xqtn37w@mbp>
Date:   Wed, 9 Jan 2019 11:31:26 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Prateek Patel <prpatel@...dia.com>
Cc:     paul@...l-moore.com, sds@...ho.nsa.gov, eparis@...isplace.org,
        linux-kernel@...r.kernel.org, selinux@...r.kernel.org,
        linux-tegra@...r.kernel.org, talho@...dia.com, swarren@...dia.com,
        linux-mm@...ck.org, snikam@...dia.com, vdumpa@...dia.com,
        Sri Krishna chowdary <schowdary@...dia.com>
Subject: Re: [PATCH] selinux: avc: mark avc node as not a leak

Hi Prateek,

On Wed, Jan 09, 2019 at 02:09:22PM +0530, Prateek Patel wrote:
> From: Sri Krishna chowdary <schowdary@...dia.com>
> 
> kmemleak detects allocated objects as leaks if not accessed for
> default scan time. The memory allocated using avc_alloc_node
> is freed using rcu mechanism when nodes are reclaimed or on
> avc_flush. So, there is no real leak here and kmemleak_scan
> detects it as a leak which is false positive. Hence, mark it as
> kmemleak_not_leak.

In theory, kmemleak should detect the node->rhead in the lists used by
call_rcu() and not report it as a leak. Which RCU options do you have
enabled (just to check whether kmemleak tracks the RCU internal lists)?

Also, does this leak eventually disappear without your patch? Does

  echo dump=0xffffffc0dd1a0e60 > /sys/kernel/debug/kmemleak

still display this object?

Thanks.

-- 
Catalin