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Tue, 03 Jan 2023 03:24:13 -0800 (PST) Received: from [192.168.1.195] ([5.133.47.210]) by smtp.googlemail.com with ESMTPSA id r17-20020a05600c425100b003cffd3c3d6csm39874902wmm.12.2023.01.03.03.24.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Jan 2023 03:24:12 -0800 (PST) Message-ID: <6b7d1e08-e27e-3f8a-5b08-ba622f206295@linaro.org> Date: Tue, 3 Jan 2023 11:24:11 +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] nvmem: core: Fix race in nvmem_register() To: Hector Martin Cc: Sven Peter , Alyssa Rosenzweig , asahi@lists.linux.dev, linux-kernel@vger.kernel.org, Russell King References: <20221214142952.9372-1-marcan@marcan.st> Content-Language: en-US From: Srinivas Kandagatla In-Reply-To: <20221214142952.9372-1-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 Thanks Hector for the patch, On 14/12/2022 14:29, 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") > Signed-off-by: Hector Martin Missing Cc Stable > --- > drivers/nvmem/core.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) > > diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c > index 321d7d63e068..d255feca5e17 100644 > --- a/drivers/nvmem/core.c > +++ b/drivers/nvmem/core.c > @@ -837,20 +837,16 @@ 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; > + return ERR_PTR(rval); you can not do this as this will leak ida and nvmem itself. > } > > if (config->compat) { > rval = nvmem_sysfs_setup_compat(nvmem, config); > if (rval) > - goto err_device_del; > + return ERR_PTR(rval); same here. > } > > if (config->cells) { > @@ -867,19 +863,21 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) > if (rval) > goto err_remove_cells; > > + rval = device_register(&nvmem->dev); > + if (rval) > + goto err_put_device; > + > blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem); > > return nvmem; > > +err_put_device: > + put_device(&nvmem->dev); this will free nvmem and further down you are going to de-reference the freed pointer. --srini > err_remove_cells: > nvmem_device_remove_all_cells(nvmem); > 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); > > return ERR_PTR(rval); > } > -- > 2.35.1 >