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d="scan'208";a="55028083" Received: from mail-pg1-f199.google.com ([209.85.215.199]) by smtp-lax3-1.ucr.edu with ESMTP/TLS/ECDHE-RSA-AES128-GCM-SHA256; 19 Jul 2021 12:24:41 -0700 Received: by mail-pg1-f199.google.com with SMTP id z30-20020a630a5e0000b029022c78a7fc98so15796284pgk.11 for ; Mon, 19 Jul 2021 12:24:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+KRwBQYkzx1TnPP604PZP7mAiiyDknEAGOzKz5P9lLk=; b=q0iu00S7Pfb4i6LpBQ+U4cgZl3+e8f4dYaB0pRYArgtd3Y1HKAWgpLVyAcJm9LrNcg fZz+bkk0o6HjIdGkHf8/CyYKIm0DRg11EsJo1wvhv5yfSC8zmAkxR+zJUC4bll6G7P8m xpRljWtzu1WWxVmE9KTZgL39CHG8z+DCOg8oqqNr5fKl7K39khnhEL+Y8LyQBtujf99j bqmLga5D1lGW/i6f6KuJ6hzANrvWe6vCqOk47EOcfYPNmKxECaUSG06dQkmFV7f3913b WbwJm12kairPO4362c/Yv1z5C/I+eSgdPbHxufJh5rj5KexdRk99nNkTiMZDZCQdYphh ziGQ== X-Gm-Message-State: AOAM53173bD2dp5DFQp9ui8N5YNYh/FoZQwIOf3p/B81ODhHoJiNaW2C wFyOhrLb62dtOVPnDpYW7/02ESMz1abe80ThaJ45V2EdG9A29CLd+nrgB/P1NMdWn+Mzztb6kyz qiozd8fk+fqtkZaDk1mfvoo609ihha4sFa62Izg== X-Received: by 2002:a62:dd83:0:b029:2e8:e511:c32f with SMTP id w125-20020a62dd830000b02902e8e511c32fmr27277331pff.49.1626722680595; Mon, 19 Jul 2021 12:24:40 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwg1RfsGvJK2QTY7aIp7/ssMd+mZmtyz3pP+qeB4sZSXtRJsKg7sA+dBra8jH9enCR2M+si7DTkxfIgrV3iMtc= X-Received: by 2002:a62:dd83:0:b029:2e8:e511:c32f with SMTP id w125-20020a62dd830000b02902e8e511c32fmr27277313pff.49.1626722680291; Mon, 19 Jul 2021 12:24:40 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Yizhuo Zhai Date: Mon, 19 Jul 2021 12:24:29 -0700 Message-ID: Subject: Re: Uninitialized Variable Use in drivers/iio/adc/stm32-dfsdm-adc.c To: Alexandru Ardelean Cc: Jonathan Cameron , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , Maxime Coquelin , Alexandre Torgue , linux-iio Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org Alexandru: Thanks for your detailed explanation, I would submit the patch accordingly. >>Just curious: are you seeing any issues with these variables being uninitialized? This bug is reported by the static analysis tool, we haven't dynamically triggered it. On Mon, Jul 19, 2021 at 12:47 AM Alexandru Ardelean wrote: > > On Mon, Jul 19, 2021 at 2:39 AM Yizhuo Zhai wrote: > > > > Hi All: > > Inside function stm32_dfsdm_irq(), the variable "status", "int_en" > > could be uninitialized if the regmap_read() fails and returns an error > > code. However, they are directly used in the later context to decide > > the control flow, which is potentially unsafe. However, > > stm32_dfsdm_irq() returns the type irqreturn_t and I could not return > > Just curious: are you seeing any issues with these variables being > uninitialized? > > > the error code directly. Could you please advise me here? > > The correct way to do it, would be: > > ret = regmap_read(regmap, DFSDM_ISR(adc->fl_id), &status); > if (ret) > return IRQ_HANDLED; > > IRQ handlers should return one of > enum irqreturn { > IRQ_NONE = (0 << 0), > IRQ_HANDLED = (1 << 0), > IRQ_WAKE_THREAD = (1 << 1), > }; > > If you want to fully optimize/correct this, then it may be something like: > > ret = regmap_read(regmap, DFSDM_ISR(adc->fl_id), &status); > if (ret) > return IRQ_HANDLED; > > if (status & DFSDM_ISR_REOCF_MASK) { > /* Read the data register clean the IRQ status */ > regmap_read(regmap, DFSDM_RDATAR(adc->fl_id), adc->buffer); > > // in this point, we could check for regmap_read(), but it won't make > sense; we should call the complete() handler, either way > > complete(&adc->completion); > } > > if (status & DFSDM_ISR_ROVRF_MASK) { > ret = regmap_read(regmap, DFSDM_CR2(adc->fl_id), &int_en); > if (ret) > return IRQ_HANDLED; > if (int_en & DFSDM_CR2_ROVRIE_MASK) > dev_warn(&indio_dev->dev, "Overrun detected\n"); > regmap_update_bits(regmap, DFSDM_ICR(adc->fl_id), > DFSDM_ICR_CLRROVRF_MASK, > DFSDM_ICR_CLRROVRF_MASK); > > // in this point, we could also check the ret code; but we still need > to call IRQ_HANDLED anyway; > } > > > Quite often, when regmap_read() returns errors, then something is > seriously wrong in the system. > Something else would usually fail or crash worse than this interrupt handler. > That being said, properly handling regmap_read() here is a good idea. > > > > > The related code: > > > > static irqreturn_t stm32_dfsdm_irq(int irq, void *arg) { > > unsigned int status, int_en; > > > > regmap_read(regmap, DFSDM_ISR(adc->fl_id), &status); > > regmap_read(regmap, DFSDM_CR2(adc->fl_id), &int_en); > > > > if (status & DFSDM_ISR_REOCF_MASK) {} > > if (status & DFSDM_ISR_ROVRF_MASK) {} > > } > > > > > > -- > > Kind Regards, > > > > Yizhuo Zhai > > > > Computer Science, Graduate Student > > University of California, Riverside -- Kind Regards, Yizhuo Zhai Computer Science, Graduate Student University of California, Riverside