linux-kernel - Re: [PATCH net] net: dsa: fix 'increment on 0' warning

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Date:   Sun, 26 Nov 2017 04:24:15 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     vivien.didelot@...oirfairelinux.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...oirfairelinux.com, f.fainelli@...il.com, andrew@...n.ch,
        fengguang.wu@...el.com, wfg@...ux.intel.com, lkp@...org
Subject: Re: [PATCH net] net: dsa: fix 'increment on 0' warning

From: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Date: Fri, 24 Nov 2017 11:36:06 -0500

> Setting the refcount to 0 when allocating a tree to match the number of
> switch devices it holds may cause an 'increment on 0; use-after-free',
> if CONFIG_REFCOUNT_FULL is enabled.
> 
> To fix this, do not decrement the refcount of a newly allocated tree,
> increment it when an already allocated tree is found, and decrement it
> after the probing of a switch, as done with the previous behavior.
> 
> At the same time, make dsa_tree_get and dsa_tree_put accept a NULL
> argument to simplify callers, and return the tree after incrementation,
> as most kref users like of_node_get and of_node_put do.
> 
> Fixes: 8e5bf9759a06 ("net: dsa: simplify tree reference counting")
> Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>

Applied, thanks Vivien.