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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1065EC3DA7D for ; Tue, 3 Jan 2023 12:41:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233301AbjACMlM (ORCPT ); Tue, 3 Jan 2023 07:41:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232753AbjACMlI (ORCPT ); Tue, 3 Jan 2023 07:41:08 -0500 Received: from mail-wm1-x331.google.com (mail-wm1-x331.google.com [IPv6:2a00:1450:4864:20::331]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB2AC10551 for ; Tue, 3 Jan 2023 04:41:03 -0800 (PST) Received: by mail-wm1-x331.google.com with SMTP id z8-20020a05600c220800b003d33b0bda11so16465263wml.0 for ; Tue, 03 Jan 2023 04:41:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=1gkN1S5ZlvpEeBogO6vpEZy9U0i82QGUm+UbrTpiEso=; b=E3K3wLQAZdncIqzqu2Q6Bd7JKdI4Rq6ZX1HiGGEj2M+BQDEGbUHwucomhqO4uZgAOD Enqs8wqSbmv0BnVfWnfZUa0Z0TpWoKe4gZTSOv666zhzqtwzFzWVj88cUO/aANoaGHiL JS+PW9W4Ql6HYCij65Wvofyolx0dHO5n+XYCd8yP8i8XEaJsO2N0lsaq1+hSB4GXLkqm 7f7uzOLgC/0y55PxKdaIh6ikINaZYWDO7WnPEgqKH903WesXJtV2E9n+2pWfEcBqNQ7K SmREjXv2EbolfNtTebVuh1CArMiBIbCLedw3I4Vu0oqrnEaB3MEQOwDpoVnYTiEaMvlA iHyg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=1gkN1S5ZlvpEeBogO6vpEZy9U0i82QGUm+UbrTpiEso=; b=dr9GOnOm4jNv/fqK7VaY4fmc2iMgKbhoxyvlwA4/S/2gn6fnmnKM3SRRnERR9yd4xd 3RNXrubiZMQ2uNVJggxbDw0T1JlyQJyPCr8f6JuMbt6YV72fki51QKGQ7KYBpAEssAxb +98oih/3YhA9G6yQ0YwwPJ16UPqlgU+j0w5hYiYoh1fGa592MPOWIqHbH5U1N5h5y+JC yBVDIVlUHSWJEv8ZgO3SwDM/utqpcB/0qZdkrfDMPCYv6Os9iLOUfjvyzHHedMnu8nzh JPjjP3femgDCwZVfi9ny2T+0LHpt9Nf3xF+XxgLmZ/cNHQyuqobYDa9D+yWBQKR48+au pbcA== X-Gm-Message-State: AFqh2kp1vakVhmDtpWpduU9hb84dZOVkJQ/mXg8lUZFA6mKdFclinAjX VeIoEmy235QCZw3YxB31twD+/g== X-Google-Smtp-Source: AMrXdXtd/n4T7oT7EJwzPIPADbEUarUVmVBN9kaC29mimSQ3fmwKsrjWYJugvfguwY0xNRU+WSG49w== X-Received: by 2002:a05:600c:798:b0:3d3:5737:3b0f with SMTP id z24-20020a05600c079800b003d357373b0fmr38639588wmo.36.1672749662438; Tue, 03 Jan 2023 04:41:02 -0800 (PST) Received: from [192.168.1.195] ([5.133.47.210]) by smtp.googlemail.com with ESMTPSA id bi14-20020a05600c3d8e00b003d9ad6783b1sm11844502wmb.6.2023.01.03.04.41.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Jan 2023 04:41:01 -0800 (PST) Message-ID: Date: Tue, 3 Jan 2023 12:41:00 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH v2] nvmem: core: Fix race in nvmem_register() Content-Language: en-US To: Hector Martin Cc: Sven Peter , Alyssa Rosenzweig , asahi@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Eric Curtin References: <20230103114427.1825-1-marcan@marcan.st> From: Srinivas Kandagatla In-Reply-To: <20230103114427.1825-1-marcan@marcan.st> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/01/2023 11:44, Hector Martin wrote: > nvmem_register() currently registers the device before adding the nvmem > cells, which creates a race window where consumers may find the nvmem > device (and not get PROBE_DEFERred), but then fail to find the cells and > error out. > > Move device registration to the end of nvmem_register(), to close the > race. > > Observed when the stars line up on Apple Silicon machines with the (not > yet upstream, but trivial) spmi nvmem driver and the macsmc-rtc client: > > [ 0.487375] macsmc-rtc macsmc-rtc: error -ENOENT: Failed to get rtc_offset NVMEM cell > > Fixes: eace75cfdcf7 ("nvmem: Add a simple NVMEM framework for nvmem providers") > Cc: stable@vger.kernel.org > Reviewed-by: Eric Curtin > Signed-off-by: Hector Martin > --- What has changed since v1? > drivers/nvmem/core.c | 32 +++++++++++++++++--------------- > 1 file changed, 17 insertions(+), 15 deletions(-) > > diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c > index 321d7d63e068..606f428d6292 100644 > --- a/drivers/nvmem/core.c > +++ b/drivers/nvmem/core.c > @@ -822,11 +822,8 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) > break; > } > > - if (rval) { > - ida_free(&nvmem_ida, nvmem->id); > - kfree(nvmem); > - return ERR_PTR(rval); > - } > + if (rval) > + goto err_gpiod_put; Why was gpiod changes added to this patch, that should be a separate patch/discussion, as this is not relevant to the issue that you are reporting. > > nvmem->read_only = device_property_present(config->dev, "read-only") || > config->read_only || !nvmem->reg_write; > @@ -837,20 +834,16 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) > > dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name); > > - rval = device_register(&nvmem->dev); > - if (rval) > - goto err_put_device; > - > if (nvmem->nkeepout) { > rval = nvmem_validate_keepouts(nvmem); > if (rval) > - goto err_device_del; > + goto err_gpiod_put; > } > > if (config->compat) { > rval = nvmem_sysfs_setup_compat(nvmem, config); > if (rval) > - goto err_device_del; > + goto err_gpiod_put; > } > > if (config->cells) { > @@ -867,6 +860,15 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) > if (rval) > goto err_remove_cells; > > + rval = device_register(&nvmem->dev); > + if (rval) { > + nvmem_device_remove_all_cells(nvmem); > + if (config->compat) > + nvmem_sysfs_remove_compat(nvmem, config); > + put_device(&nvmem->dev); > + return ERR_PTR(rval); > + } > + > blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem); > > return nvmem; > @@ -876,10 +878,10 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) > err_teardown_compat: > if (config->compat) > nvmem_sysfs_remove_compat(nvmem, config); > -err_device_del: > - device_del(&nvmem->dev); > -err_put_device: > - put_device(&nvmem->dev); > +err_gpiod_put: > + gpiod_put(nvmem->wp_gpio); > + ida_free(&nvmem_ida, nvmem->id); > + kfree(nvmem); > > return ERR_PTR(rval); > } > -- > 2.35.1 >