netdev - Re: [PATCH] macb: Don't unregister clks unconditionally

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Message-Id: <20200105.151125.1541050812175137787.davem@davemloft.net>
Date:   Sun, 05 Jan 2020 15:11:25 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     sboyd@...nel.org
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        nicolas.ferre@...rochip.com, yash.shah@...ive.com,
        linux@...ck-us.net
Subject: Re: [PATCH] macb: Don't unregister clks unconditionally

From: Stephen Boyd <sboyd@...nel.org>
Date: Fri,  3 Jan 2020 16:19:21 -0800

> The only clk init function in this driver that register a clk is
> fu540_c000_clk_init(), and thus we need to unregister the clk when this
> driver is removed on that platform. Other init functions, for example
> macb_clk_init(), don't register clks and therefore we shouldn't
> unregister the clks when this driver is removed. Convert this
> registration path to devm so it gets auto-unregistered when this driver
> is removed and drop the clk_unregister() calls in driver remove (and
> error paths) so that we don't erroneously remove a clk from the system
> that isn't registered by this driver.
> 
> Otherwise we get strange crashes with a use-after-free when the
> devm_clk_get() call in macb_clk_init() calls clk_put() on a clk pointer
> that has become invalid because it is freed in clk_unregister().
> 
> Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>
> Cc: Yash Shah <yash.shah@...ive.com>
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Fixes: c218ad559020 ("macb: Add support for SiFive FU540-C000")
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>

Applied and queued up for -stable, thanks.