From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE342C43461 for ; Thu, 10 Sep 2020 22:15:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DE98208E4 for ; Thu, 10 Sep 2020 22:15:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gkuqVsTi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725379AbgIJWPw (ORCPT ); Thu, 10 Sep 2020 18:15:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725294AbgIJWPu (ORCPT ); Thu, 10 Sep 2020 18:15:50 -0400 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B113FC061573 for ; Thu, 10 Sep 2020 15:15:49 -0700 (PDT) Received: by mail-wr1-x441.google.com with SMTP id c18so9036457wrm.9 for ; Thu, 10 Sep 2020 15:15:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=xL46EKHdUAe28O/xpV5/mdAjbLeGwABswJE/jPWXDpU=; b=gkuqVsTizd3Iy1tD9bOeuDijPrrHbfVSg97mseZZ9jCGb3z9klNUQzdHOwbj06Xtvi 7oioRJHtOQRBXt0846A/AAip9hWl88KWda5HQQ2SdiZsSN933ILMfumdrXs2ieSDDF+V gNv8iV1+KPbpsiIV0Y1jhYErQKH/Xxh8FdgkM2K68RIg3hDUEQdAJy9kKRkSFCtim7K7 vOo2XJ16YYD6Ms3tkcid+L+yZbaln0nTlSvnci9k0B/p7ojj5d7HAzRNssZUczlebZBz VT5lOTLZ4bWMT2AnQqVj1qREwNzHTojWY3gIhXFQtT8gIEAGCt/3cy40PPda8TuOEvFW kdrg== 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=xL46EKHdUAe28O/xpV5/mdAjbLeGwABswJE/jPWXDpU=; b=C4jBByfHdj1EmJ7vwOvk/utbcwViufkF1rEXca8mtZ9tgMM0H4sncZMqCRZeprabjl yORUvCZB5X58tJldRph9Gi1tM/Wzu6Yv/wVHnYAAruh3H++aRAN04lDWe4QQevqh8EXX 34+4x56TSyJdQmCzBoEiQ4b9PaCvdHxTYsseUyI5kXVugvGr3N6DemrbpGp6JZ0wgljb M1uTvbQLqH+5DksGvnRN5MWdvehui+nRbgi50Oetzs8wk4A5QeM1o8BrFoLYNnTftOH5 un+otBZVxiGbCj4usubunb0u2IrMsXAz6XXONJKUFBhYzggLRtvk69nHTf/QfHC42Wx5 110A== X-Gm-Message-State: AOAM530U8wU7yTFc8hqxAkygklPXa1uZFrnBTq+BivWB1yMf0tXvBHdr t2/X6rc5b1bg1uOQ9NwRoDKSn51V6h5bHVcRwOI= X-Google-Smtp-Source: ABdhPJwTVP6cjq4eEIv/cwbf/GNJtz0o80yCatHKXmdR3M24trCTRDY7nMTwOP9CrE/Uu79wbMfda7NhwyV+PYG3PNs= X-Received: by 2002:a5d:4d82:: with SMTP id b2mr10782749wru.232.1599776148263; Thu, 10 Sep 2020 15:15:48 -0700 (PDT) MIME-Version: 1.0 References: <20200908072400.GB294938@mwanda> In-Reply-To: <20200908072400.GB294938@mwanda> From: Andrey Smirnov Date: Thu, 10 Sep 2020 15:15:36 -0700 Message-ID: Subject: Re: [bug report] spi: gpio: Use devm_spi_register_master() To: Dan Carpenter Cc: Navid Emamdoost , linux-spi@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org On Tue, Sep 8, 2020 at 12:24 AM Dan Carpenter wrote: > > Hello Andrey Smirnov, > > The patch 79567c1a321e: "spi: gpio: Use devm_spi_register_master()" > from Apr 2, 2019, leads to the following static checker warning: > > drivers/spi/spi-gpio.c:435 spi_gpio_probe() > warn: 'master->dev.kobj' not decremented on lines: 435. > > drivers/spi/spi-gpio.c > 358 static int spi_gpio_probe(struct platform_device *pdev) > 359 { > 360 int status; > 361 struct spi_master *master; > 362 struct spi_gpio *spi_gpio; > 363 struct device *dev = &pdev->dev; > 364 struct spi_bitbang *bb; > 365 > 366 master = spi_alloc_master(dev, sizeof(*spi_gpio)); > 367 if (!master) > 368 return -ENOMEM; > 369 > 370 status = devm_add_action_or_reset(&pdev->dev, spi_gpio_put, master); > 371 if (status) { > 372 spi_master_put(master); > ^^^^^^^^^^^^^^^^^^^^^^ > The devm_add_action_or_reset() function calls spi_gpio_put() on error > so this seems like a double free. > This does look like a double free. Can't comment on the logic behind it, that's a change Navid made, so I'll let him speak for it. > 373 return status; > 374 } > 375 > 376 if (pdev->dev.of_node) > 377 status = spi_gpio_probe_dt(pdev, master); > 378 else > 379 status = spi_gpio_probe_pdata(pdev, master); > 380 > 381 if (status) > 382 return status; > 383 > 384 spi_gpio = spi_master_get_devdata(master); > 385 > 386 status = spi_gpio_request(dev, spi_gpio); > 387 if (status) > 388 return status; > 389 > 390 master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32); > 391 master->mode_bits = SPI_3WIRE | SPI_3WIRE_HIZ | SPI_CPHA | SPI_CPOL | > 392 SPI_CS_HIGH; > 393 if (!spi_gpio->mosi) { > 394 /* HW configuration without MOSI pin > 395 * > 396 * No setting SPI_MASTER_NO_RX here - if there is only > 397 * a MOSI pin connected the host can still do RX by > 398 * changing the direction of the line. > 399 */ > 400 master->flags = SPI_MASTER_NO_TX; > 401 } > 402 > 403 master->bus_num = pdev->id; > 404 master->setup = spi_gpio_setup; > 405 master->cleanup = spi_gpio_cleanup; > 406 > 407 bb = &spi_gpio->bitbang; > 408 bb->master = master; > 409 /* > 410 * There is some additional business, apart from driving the CS GPIO > 411 * line, that we need to do on selection. This makes the local > 412 * callback for chipselect always get called. > 413 */ > 414 master->flags |= SPI_MASTER_GPIO_SS; > 415 bb->chipselect = spi_gpio_chipselect; > 416 bb->set_line_direction = spi_gpio_set_direction; > 417 > 418 if (master->flags & SPI_MASTER_NO_TX) { > 419 bb->txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0; > 420 bb->txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1; > 421 bb->txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2; > 422 bb->txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3; > 423 } else { > 424 bb->txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; > 425 bb->txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; > 426 bb->txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; > 427 bb->txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3; > 428 } > 429 bb->setup_transfer = spi_bitbang_setup_transfer; > 430 > 431 status = spi_bitbang_init(&spi_gpio->bitbang); > 432 if (status) > 433 return status; > 434 > 435 return devm_spi_register_master(&pdev->dev, spi_master_get(master)); > ^^^^^^^^^^^^^^^^^^^^^^ > Why are we taking a second reference here? Where will it be released? > This additional reference taking came from inlining of the code from spi_bitbang_start(): https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/spi/spi-bitbang.c?h=v5.9-rc4#n405 and the logic behind reference taking seems to have come from this change: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers?h=v5.9-rc4&id=702a4879ec337463f858c8ab467482cce260bf18 Release should happen once devres action registered by > 370 status = devm_add_action_or_reset(&pdev->dev, spi_gpio_put, master); is executed upon devres "unwinding", see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers?h=v5.9-rc4&id=8b797490b4db09492acda4b4a4a4355d2311a614 At least I think that what my thinking was for making that change.