linux-kernel - Re: [PATCH] pwm: stm32: Fix the usage of uninitialized variable in stm32_pwm

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Message-ID: <20191004062336.jidzrytx4z5talro@pengutronix.de>
Date:   Fri, 4 Oct 2019 08:23:36 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Yizhuo <yzhai003@....edu>
Cc:     Fabrice Gasnier <fabrice.gasnier@...com>,
        Thierry Reding <thierry.reding@...il.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        linux-pwm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pwm: stm32: Fix the usage of uninitialized variable in
 stm32_pwm_config()

Hello,

On Thu, Oct 03, 2019 at 09:46:49PM -0700, Yizhuo wrote:
> Inside function stm32_pwm_config(), variable "psc" and " arr"
> could be uninitialized if regmap_read() returns -EINVALs.
> However, they are used later in the if statement to decide
> the return value which is potentially unsafe.
> 
> The same case happens in function stm32_pwm_detect_channels()
> with variable "ccer", but we cannot just return -EINVAL because
> the error code is not acceptable by the caller. Aslo, the variable

s/Aslo/Also/

> "ccer" in functionstm32_pwm_detect_complementary() could also be

s/functionstm32_pwm_detect_/function stm32_pwm_detect_/

> uninitialized, since stm32_pwm_detect_complementary() returns void,
> the patch is not easy.

active_channels() is also affected. Also there are calls to
regmap_update_bits which should have their return values checked.

While a patch to fix these all is not trivial it is certainly possible
and I would prefer to fix the problem completely.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |