From nobody Fri Dec 19 15:33:27 2025 Received: from mail-wm1-f49.google.com (mail-wm1-f49.google.com [209.85.128.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E242014AB1 for ; Tue, 2 Jan 2024 15:59:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=bgdev.pl Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bgdev.pl Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bgdev-pl.20230601.gappssmtp.com header.i=@bgdev-pl.20230601.gappssmtp.com header.b="I/F8dAhF" Received: by mail-wm1-f49.google.com with SMTP id 5b1f17b1804b1-40d5aefcc2fso55870685e9.0 for ; Tue, 02 Jan 2024 07:59:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bgdev-pl.20230601.gappssmtp.com; s=20230601; t=1704211194; x=1704815994; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=qgJ68qs44Lcqe8TCw142wLnFP4mWeBCuDvsZcDC2Hj8=; b=I/F8dAhFXk0gDICtKIkqAqTnOg96FpLU0X46Glli0PXSC2kBkyfsfY1S5YqNULZXPI yPPQ57I2EQom14KzZ+ffs/HGpgeHfuEnDbP4wR8D4udgWEYefmk+4i2UBs2wjXgzjgnA /UnINcjnZdYKpb11EhtDot1WGNtDhANBfXT4eblPeC8QCmhf1o7r0BVOr787RqTU3k2z d8sJEfrmlrwxIR1Af6XCD76n5XYmf046A3X/vXhy0x8iG/amMqQVMiWGlaUO2XUa4rN9 +16AIIattoOlPqoSlGKGiHViiq4rMlRVD+cgiKxIwhOA8G3Gmcoqf1m6VLPQRTld2OOX TWJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704211194; x=1704815994; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qgJ68qs44Lcqe8TCw142wLnFP4mWeBCuDvsZcDC2Hj8=; b=VKjGfm9ro9PPZp3x2rWL2Sz3vGr1kRyPvJivgJ8+9SHMt3vemKkkiib1tsfVD5xaMh IMCoEn8lHL+nCeHJXTV1sCDtaDcbtv13FZUIhNrApHCm/5IrffuvmEatweNcSzBhzqX7 jkaD6BfdFUcK1nQf4NthNcUk4yUSd7bnBzvp18cejUjKME2sGHhm2x+997HrfuDvWdVz 9BS9xrBV0YEUbG9Hah0osyiT398t0NO6NXZFW5za8Kzibt3m7azB+0HX4R+Xbr0dorcc peuMSRtqRPwkbH1fhV6Gn08eUr3H/jFznELjC79b8qMkmRwIuilQToyz1u9E59klNVPm fvqA== X-Gm-Message-State: AOJu0YxLxK+Ejs1JGHKTaesfIhp5OmBkCXrgLq5OQa/b3bsTiLOHpFtP kzqC6/25z/lWmQh/q033bG15a21iCpkdFCDn4vgmydYFUrk= X-Google-Smtp-Source: AGHT+IEIx7iO4O+2hI4WmFZMKnVPkhvLRQqC9aD3ixvuGIyV3qeFn4DGO8oPt33bW+FY9YKuPLQNTg== X-Received: by 2002:a05:600c:2a8d:b0:40c:610e:3c69 with SMTP id x13-20020a05600c2a8d00b0040c610e3c69mr9638192wmd.36.1704211194128; Tue, 02 Jan 2024 07:59:54 -0800 (PST) Received: from brgl-uxlite.home ([2a01:cb1d:334:ac00:6f51:fa47:f00a:a53c]) by smtp.gmail.com with ESMTPSA id u14-20020a05600c138e00b0040d62f97e3csm20556641wmf.10.2024.01.02.07.59.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Jan 2024 07:59:53 -0800 (PST) From: Bartosz Golaszewski To: Linus Walleij Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH v2 1/3] gpiolib: remove the GPIO device from the list when it's unregistered Date: Tue, 2 Jan 2024 16:59:47 +0100 Message-Id: <20240102155949.73434-2-brgl@bgdev.pl> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240102155949.73434-1-brgl@bgdev.pl> References: <20240102155949.73434-1-brgl@bgdev.pl> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Bartosz Golaszewski If we wait until the GPIO device's .release() callback gets invoked before we remove it from the global device list, then we risk that someone will look it up using gpio_device_find() between where we dropped the last reference and before .release() is done taking a reference again to an object that's being released. The device must be removed when it's being unregistered - just like how we remove it from the GPIO bus. Fixes: ff2b13592299 ("gpio: make the gpiochip a real device") Signed-off-by: Bartosz Golaszewski Reviewed-by: Linus Walleij --- drivers/gpio/gpiolib.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index e21497b989a1..e019c4243809 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -651,9 +651,6 @@ static void gpiodev_release(struct device *dev) { struct gpio_device *gdev =3D to_gpio_device(dev); =20 - scoped_guard(mutex, &gpio_devices_lock) - list_del(&gdev->list); - ida_free(&gpio_ida, gdev->id); kfree_const(gdev->label); kfree(gdev->descs); @@ -1068,6 +1065,9 @@ void gpiochip_remove(struct gpio_chip *gc) dev_crit(&gdev->dev, "REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n"); =20 + scoped_guard(mutex, &gpio_devices_lock) + list_del(&gdev->list); + /* * The gpiochip side puts its use of the device to rest here: * if there are no userspace clients, the chardev and device will --=20 2.40.1 From nobody Fri Dec 19 15:33:27 2025 Received: from mail-wm1-f41.google.com (mail-wm1-f41.google.com [209.85.128.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EEC8814ABF for ; Tue, 2 Jan 2024 15:59:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=bgdev.pl Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bgdev.pl Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bgdev-pl.20230601.gappssmtp.com header.i=@bgdev-pl.20230601.gappssmtp.com header.b="PduPRUQs" Received: by mail-wm1-f41.google.com with SMTP id 5b1f17b1804b1-40d88f9e602so14444325e9.3 for ; Tue, 02 Jan 2024 07:59:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bgdev-pl.20230601.gappssmtp.com; s=20230601; t=1704211195; x=1704815995; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=g3wf/pQ/AJWgbz0DcSp/EQGOfmOL52HnCJ3+CUimtjU=; b=PduPRUQsYm/KpfCIrEUCZUXYsQ7W+JTChiO0vxlA4tCt/TnMtN6KAmdNhvsJUnN1+9 xk6NawI3a+MvdzLGPMnsSw2Ri/H0/Zkk2YL6tte1jfjHmTyySxByGhzaZiTecbsKmjVk DHsTPO+WwUPvfXF8/AxcogXxL6p0FZGsdPO+kr+yKEw28WVDfDcmyhUgqgzwuZoq1Cvx x3yfPJGfsSSFvl1deH43Mj17jFTX+vZ2ljdRKl6vgifEzzmRhzCGeEz5v5YwyioaEboQ UlVfdZgS40bP1AqxgpXDJMIkCndRDH+LzRHzxRhQ7AaIFcZsFmSW68eUSs7Wsju8//Cq sD3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704211195; x=1704815995; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=g3wf/pQ/AJWgbz0DcSp/EQGOfmOL52HnCJ3+CUimtjU=; b=L9XnvL7PJBh5k3yoMwDY/Xwul2Ok8Gyy5g7w2pcfp7FXHh7se5ZWJsA3F50RHe9Fxw FPM02cNteZYZItl79G9eZsTqW9GBHwzj6WaagfEW5YMqOrI5mdEFT31M7wbSs4OSJtFI 5NaW1F3hH/+fScNeytx2H8usiigpzS/K06Xxiby8glnPd++kfGc7+jHS/5OWsI/bt8U6 iUNrIdfGqZtaS993AK7v8JbiB09V31VEVodgPGgSv4IvM0dHq4v3JlBSQKXMggnVW2YV R81jhTvKk7fgBL7JYeyULVulrx63nT+J2u+kBmB04KUdNz4SU+Ajd/3gnh+xtF3XHFpo IcFw== X-Gm-Message-State: AOJu0YwSbFxY6zUdttEnIhMZTctSd2UKMXm7VxrexVuO9XhGCakhv6cz 7W+U/2ZP5S63PCMoK8DnHVPOtTtXvYTDnA== X-Google-Smtp-Source: AGHT+IHPuqgldGLMFnRYL6FhPI2YLi1Eg/NCz/1AQ9quf/p1eetr/TeWu+oHiX7d0d/zVPaZOgEOSA== X-Received: by 2002:a05:600c:1ca9:b0:40d:5b0d:b105 with SMTP id k41-20020a05600c1ca900b0040d5b0db105mr6173715wms.117.1704211195108; Tue, 02 Jan 2024 07:59:55 -0800 (PST) Received: from brgl-uxlite.home ([2a01:cb1d:334:ac00:6f51:fa47:f00a:a53c]) by smtp.gmail.com with ESMTPSA id u14-20020a05600c138e00b0040d62f97e3csm20556641wmf.10.2024.01.02.07.59.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Jan 2024 07:59:54 -0800 (PST) From: Bartosz Golaszewski To: Linus Walleij Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH v2 2/3] gpiolib: replace the GPIO device mutex with a read-write semaphore Date: Tue, 2 Jan 2024 16:59:48 +0100 Message-Id: <20240102155949.73434-3-brgl@bgdev.pl> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240102155949.73434-1-brgl@bgdev.pl> References: <20240102155949.73434-1-brgl@bgdev.pl> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Bartosz Golaszewski There are only two spots where we modify (add to or remove objects from) the GPIO device list. Readers should be able to access it concurrently. Replace the mutex with a read-write semaphore and adjust the locking operations accordingly. Signed-off-by: Bartosz Golaszewski Reviewed-by: Linus Walleij --- drivers/gpio/gpiolib-sysfs.c | 2 +- drivers/gpio/gpiolib.c | 18 +++++++++--------- drivers/gpio/gpiolib.h | 2 +- 3 files changed, 11 insertions(+), 11 deletions(-) diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c index 2d29ae37d953..4dbf298bb5dd 100644 --- a/drivers/gpio/gpiolib-sysfs.c +++ b/drivers/gpio/gpiolib-sysfs.c @@ -773,7 +773,7 @@ int gpiochip_sysfs_register_all(void) struct gpio_device *gdev; int ret; =20 - guard(mutex)(&gpio_devices_lock); + guard(rwsem_read)(&gpio_devices_sem); =20 list_for_each_entry(gdev, &gpio_devices, list) { if (gdev->mockdev) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index e019c4243809..4c93cf73a826 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -85,7 +85,7 @@ static DEFINE_MUTEX(gpio_lookup_lock); static LIST_HEAD(gpio_lookup_list); =20 LIST_HEAD(gpio_devices); -DEFINE_MUTEX(gpio_devices_lock); +DECLARE_RWSEM(gpio_devices_sem); =20 static DEFINE_MUTEX(gpio_machine_hogs_mutex); static LIST_HEAD(gpio_machine_hogs); @@ -118,7 +118,7 @@ struct gpio_desc *gpio_to_desc(unsigned gpio) { struct gpio_device *gdev; =20 - scoped_guard(mutex, &gpio_devices_lock) { + scoped_guard(rwsem_read, &gpio_devices_sem) { list_for_each_entry(gdev, &gpio_devices, list) { if (gdev->base <=3D gpio && gdev->base + gdev->ngpio > gpio) @@ -402,7 +402,7 @@ static struct gpio_desc *gpio_name_to_desc(const char *= const name) if (!name) return NULL; =20 - guard(mutex)(&gpio_devices_lock); + guard(rwsem_read)(&gpio_devices_sem); =20 list_for_each_entry(gdev, &gpio_devices, list) { struct gpio_desc *desc; @@ -871,7 +871,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, vo= id *data, =20 gdev->ngpio =3D gc->ngpio; =20 - scoped_guard(mutex, &gpio_devices_lock) { + scoped_guard(rwsem_write, &gpio_devices_sem) { /* * TODO: this allocates a Linux GPIO number base in the global * GPIO numberspace for this chip. In the long run we want to @@ -1001,7 +1001,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, = void *data, goto err_print_message; } err_remove_from_list: - scoped_guard(mutex, &gpio_devices_lock) + scoped_guard(rwsem_write, &gpio_devices_sem) list_del(&gdev->list); err_free_label: kfree_const(gdev->label); @@ -1065,7 +1065,7 @@ void gpiochip_remove(struct gpio_chip *gc) dev_crit(&gdev->dev, "REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n"); =20 - scoped_guard(mutex, &gpio_devices_lock) + scoped_guard(rwsem_write, &gpio_devices_sem) list_del(&gdev->list); =20 /* @@ -1114,7 +1114,7 @@ struct gpio_device *gpio_device_find(void *data, */ might_sleep(); =20 - guard(mutex)(&gpio_devices_lock); + guard(rwsem_read)(&gpio_devices_sem); =20 list_for_each_entry(gdev, &gpio_devices, list) { if (gdev->chip && match(gdev->chip, data)) @@ -4730,7 +4730,7 @@ static void *gpiolib_seq_start(struct seq_file *s, lo= ff_t *pos) =20 s->private =3D ""; =20 - guard(mutex)(&gpio_devices_lock); + guard(rwsem_read)(&gpio_devices_sem); 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Tue, 02 Jan 2024 07:59:56 -0800 (PST) Received: from brgl-uxlite.home ([2a01:cb1d:334:ac00:6f51:fa47:f00a:a53c]) by smtp.gmail.com with ESMTPSA id u14-20020a05600c138e00b0040d62f97e3csm20556641wmf.10.2024.01.02.07.59.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Jan 2024 07:59:55 -0800 (PST) From: Bartosz Golaszewski To: Linus Walleij Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH v2 3/3] gpiolib: pin GPIO devices in place during descriptor lookup Date: Tue, 2 Jan 2024 16:59:49 +0100 Message-Id: <20240102155949.73434-4-brgl@bgdev.pl> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240102155949.73434-1-brgl@bgdev.pl> References: <20240102155949.73434-1-brgl@bgdev.pl> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Bartosz Golaszewski There's time between when we locate the relevant descriptor during lookup and when we actually take the reference to its parent GPIO device where - if the GPIO device in question is removed - we'll end up with a dangling pointer to freed memory. Make sure devices cannot be removed until we hold a new reference to the device. Signed-off-by: Bartosz Golaszewski Reviewed-by: Linus Walleij --- drivers/gpio/gpiolib.c | 40 +++++++++++++++++++++++----------------- 1 file changed, 23 insertions(+), 17 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 4c93cf73a826..be57f8d6aeae 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -4134,27 +4134,33 @@ static struct gpio_desc *gpiod_find_and_request(str= uct device *consumer, struct gpio_desc *desc; int ret; =20 - desc =3D gpiod_find_by_fwnode(fwnode, consumer, con_id, idx, &flags, &loo= kupflags); - if (gpiod_not_found(desc) && platform_lookup_allowed) { + scoped_guard(rwsem_read, &gpio_devices_sem) { + desc =3D gpiod_find_by_fwnode(fwnode, consumer, con_id, idx, + &flags, &lookupflags); + if (gpiod_not_found(desc) && platform_lookup_allowed) { + /* + * Either we are not using DT or ACPI, or their lookup + * did not return a result. In that case, use platform + * lookup as a fallback. + */ + dev_dbg(consumer, + "using lookup tables for GPIO lookup\n"); + desc =3D gpiod_find(consumer, con_id, idx, &lookupflags); + } + + if (IS_ERR(desc)) { + dev_dbg(consumer, "No GPIO consumer %s found\n", + con_id); + return desc; + } + /* - * Either we are not using DT or ACPI, or their lookup did not - * return a result. In that case, use platform lookup as a - * fallback. + * If a connection label was passed use that, else attempt to + * use the device name as label */ - dev_dbg(consumer, "using lookup tables for GPIO lookup\n"); - desc =3D gpiod_find(consumer, con_id, idx, &lookupflags); + ret =3D gpiod_request(desc, label); } =20 - if (IS_ERR(desc)) { - dev_dbg(consumer, "No GPIO consumer %s found\n", con_id); - return desc; - } - - /* - * If a connection label was passed use that, else attempt to use - * the device name as label - */ - ret =3D gpiod_request(desc, label); if (ret) { if (!(ret =3D=3D -EBUSY && flags & GPIOD_FLAGS_BIT_NONEXCLUSIVE)) return ERR_PTR(ret); --=20 2.40.1