From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp5-g21.free.fr ([2a01:e0c:1:1599::14]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1f40wp-0006tW-L2 for linux-mtd@lists.infradead.org; Thu, 05 Apr 2018 09:12:49 +0000 Subject: Re: [PATCH 1/1] mtd:nand:fix memory leak To: Boris Brezillon , Miquel Raynal Cc: Xidong Wang , Mans Rullgard , Marek Vasut , Richard Weinberger , Cyrille Pitchen , Brian Norris , David Woodhouse , linux-mtd References: <1522811151-18853-1-git-send-email-wangxidong_97@163.com> <20180404082807.0f211578@xps13> <20180404090710.4f74b5b4@bbrezillon> <20180404090831.37e85d59@bbrezillon> From: Marc Gonzalez Message-ID: <6ae95633-d82f-1294-c7c7-db59c00d1d4d@free.fr> Date: Thu, 5 Apr 2018 11:12:11 +0200 MIME-Version: 1.0 In-Reply-To: <20180404090831.37e85d59@bbrezillon> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 04/04/2018 09:08, Boris Brezillon wrote: > On Wed, 4 Apr 2018 09:07:10 +0200 > Boris Brezillon wrote: > >> On Wed, 4 Apr 2018 08:28:07 +0200 >> Miquel Raynal wrote: >> >>> Hi Xidong, >>> >>> As part of a reorganization in the NAND subsystem, you should now >>> prefix your commit title this way: >>> >>> mtd: rawnand: tango: fix memory leak >>> >>> Not sure if this patch is candidate to cc:stable? >>> >>> On Wed, 4 Apr 2018 11:05:51 +0800, Xidong Wang >>> wrote: >>> >>>> In function tango_nand_probe(), the memory allocated by >>>> clk_get() is not released on the normal path and >>>> the error path that IS_ERR(nfc->chan) returns true. >>> >>> The fact that the error path returns true looks out of topic, can you >>> remove it? Just saying that you fix a memory leak is enough I guess. >>> >>>> This will result in a memory leak bug. >>>> >>>> Signed-off-by: Xidong Wang >>>> --- >>>> drivers/mtd/nand/tango_nand.c | 5 ++++- >>>> 1 file changed, 4 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/mtd/nand/tango_nand.c b/drivers/mtd/nand/tango_nand.c >>>> index c5bee00b..8083459 100644 >>>> --- a/drivers/mtd/nand/tango_nand.c >>>> +++ b/drivers/mtd/nand/tango_nand.c >>>> @@ -648,12 +648,15 @@ static int tango_nand_probe(struct platform_device *pdev) >>>> return PTR_ERR(clk); >>>> >>>> nfc->chan = dma_request_chan(&pdev->dev, "rxtx"); >>>> - if (IS_ERR(nfc->chan)) >>>> + if (IS_ERR(nfc->chan)) { >>>> + clk_put(clk); >>>> return PTR_ERR(nfc->chan); >>>> + } >>>> >>>> platform_set_drvdata(pdev, nfc); >>>> nand_hw_control_init(&nfc->hw); >>>> nfc->freq_kHz = clk_get_rate(clk) / 1000; >>>> + clk_put(clk); >>> >>> If the clock is used only here, better do the frequency derivation >>> right after the clock_get(), and follow with a clk_put()? This way you >>> don't have to change the error path and 'related' actions remain >>> grouped. >> >> Hm, definitely not a good idea to release the reference you have on the >> clk if the driver depends on it. I recommend using devm_clk_get() to >> solve this leak. > > BTW, it's also weird that the driver does not prepare_enable the clk. > Marc, any comments? I was not aware that clk_get() allocated memory, and required clk_put() for cleanup. IIRC, I looked at Documentation/clk.txt On tango, clocks are configured by the boot loader. The existing clk driver provides only read access to various clocks -- except the CPU clock, which can be changed by tweaking a post-divider. Tweaking the PLLs requires much more complex code. The boot loader enables every clock, and Linux has no way to gate any of them. In the nfc driver, all I needed was the system frequency, since the NFC is driven by the system clock (which can never be disabled). Thus, I wrote the naive (and apparently incorrect) clk = clk_get(&pdev->dev, NULL); nfc->freq_kHz = clk_get_rate(clk) / 1000; I suppose the following patch would fix the memory leak, and matches what Miquèl suggested. Regards. diff --git a/drivers/mtd/nand/tango_nand.c b/drivers/mtd/nand/tango_nand.c index c5bee00b7f5e..fba162af333f 100644 --- a/drivers/mtd/nand/tango_nand.c +++ b/drivers/mtd/nand/tango_nand.c @@ -646,6 +646,8 @@ static int tango_nand_probe(struct platform_device *pdev) clk = clk_get(&pdev->dev, NULL); if (IS_ERR(clk)) return PTR_ERR(clk); + nfc->freq_kHz = clk_get_rate(clk) / 1000; + clk_put(clk); nfc->chan = dma_request_chan(&pdev->dev, "rxtx"); if (IS_ERR(nfc->chan)) @@ -653,7 +655,6 @@ static int tango_nand_probe(struct platform_device *pdev) platform_set_drvdata(pdev, nfc); nand_hw_control_init(&nfc->hw); - nfc->freq_kHz = clk_get_rate(clk) / 1000; for_each_child_of_node(pdev->dev.of_node, np) { err = chip_init(&pdev->dev, np);