linux-kernel - Re: [PATCH 2/2] tty: serial: samsung_tty: Fix a memory leak in s3c24xx_serial

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Message-ID: <20230610103958.jwfe45zm52ehiovn@intel.intel>
Date:   Sat, 10 Jun 2023 12:39:58 +0200
From:   Andi Shyti <andi.shyti@...nel.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Thomas Abraham <thomas.abraham@...aro.org>,
        Kukjin Kim <kgene.kim@...sung.com>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH 2/2] tty: serial: samsung_tty: Fix a memory leak in
 s3c24xx_serial_getclk() when iterating clk

Hi Christophe,

On Fri, Jun 09, 2023 at 06:45:39AM +0200, Christophe JAILLET wrote:
> When the best clk is searched, we iterate over all possible clk.
> 
> If we find a better match, the previous one, if any, needs to be freed.
> If a better match has already been found, we still need to free the new
> one, otherwise it leaks.
> 
> Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> This patch is speculative. Review with care.
> 
> I think that some clk_put() are also missing somewhere else in the driver
> but won't be able to investigate further.
> ---
>  drivers/tty/serial/samsung_tty.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index dd751e7010e3..c07877dd25fa 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -1488,10 +1488,18 @@ static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
>  			calc_deviation = -calc_deviation;
>  
>  		if (calc_deviation < deviation) {
> +			/*
> +			 * If we find a better clk, release the previous one, if
> +			 * any.
> +			 */
> +			if (!IS_ERR(*best_clk))

what is the case when *best_clk has an error in it?

Andi

> +				clk_put(*best_clk);
>  			*best_clk = clk;
>  			best_quot = quot;
>  			*clk_num = cnt;
>  			deviation = calc_deviation;
> +		} else {
> +			clk_put(clk);
>  		}
>  	}
>  
> -- 
> 2.34.1
>