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 AF5CEC4332F for ; Tue, 31 Oct 2023 09:27:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343792AbjJaJ1E (ORCPT ); Tue, 31 Oct 2023 05:27:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343853AbjJaJ1D (ORCPT ); Tue, 31 Oct 2023 05:27:03 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 192D6DA for ; Tue, 31 Oct 2023 02:26:55 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73603C433C7; Tue, 31 Oct 2023 09:26:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698744414; bh=zKOoMaM7RaTJGquT1LPKFtV1D7fRX3uHAxHcTPD90bM=; h=From:To:Cc:Subject:Date:From; b=FPizzltaC8CeztY2XsUpi0dUNQTVPTnACVtcgOsDb068ioyaWMEGqUScsUGGRCJ9m SQAiARHeWrLCQlunxhaE5ysvPI2A0cnZ1DdeC2SOo0Ip7JrfSUi3oI7QgGteGKE69H t6CU1i/e2J6UbN6eYEd7YhCoIXlycDj3ah+ZOierpp/iaVcHtYrpxR7E5cdtcHpwOy hPZQD303CBb1Z1M+4430UnTCho3Fr05xXwHE6My1X/bnhpJGV4BoRsidEupg5O+6Jy yYI5pHOmnI2zHNdCZzJDEJlGmhBmry95edS68viDaJbO5cU2LaBXCRYRXSCK6Hb5eK OpD6qEENiU6wA== From: Lee Jones To: lee@kernel.org Cc: stable@vger.kernel.org, Krzysztof Kozlowski , "Rafael J . Wysocki" , Greg Kroah-Hartman Subject: [PATCH v5.4.y 1/6] driver: platform: Add helper for safer setting of driver_override Date: Tue, 31 Oct 2023 09:26:35 +0000 Message-ID: <20231031092645.2230861-1-lee@kernel.org> X-Mailer: git-send-email 2.42.0.820.g83a721a137-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Krzysztof Kozlowski commit 6c2f421174273de8f83cde4286d1c076d43a2d35 upstream. Several core drivers and buses expect that driver_override is a dynamically allocated memory thus later they can kfree() it. However such assumption is not documented, there were in the past and there are already users setting it to a string literal. This leads to kfree() of static memory during device release (e.g. in error paths or during unbind): kernel BUG at ../mm/slub.c:3960! Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM ... (kfree) from [] (platform_device_release+0x88/0xb4) (platform_device_release) from [] (device_release+0x2c/0x90) (device_release) from [] (kobject_put+0xec/0x20c) (kobject_put) from [] (exynos5_clk_probe+0x154/0x18c) (exynos5_clk_probe) from [] (platform_drv_probe+0x6c/0xa4) (platform_drv_probe) from [] (really_probe+0x280/0x414) (really_probe) from [] (driver_probe_device+0x78/0x1c4) (driver_probe_device) from [] (bus_for_each_drv+0x74/0xb8) (bus_for_each_drv) from [] (__device_attach+0xd4/0x16c) (__device_attach) from [] (bus_probe_device+0x88/0x90) (bus_probe_device) from [] (device_add+0x3dc/0x62c) (device_add) from [] (of_platform_device_create_pdata+0x94/0xbc) (of_platform_device_create_pdata) from [] (of_platform_bus_create+0x1a8/0x4fc) (of_platform_bus_create) from [] (of_platform_bus_create+0x20c/0x4fc) (of_platform_bus_create) from [] (of_platform_populate+0x84/0x118) (of_platform_populate) from [] (of_platform_default_populate_init+0xa0/0xb8) (of_platform_default_populate_init) from [] (do_one_initcall+0x8c/0x404) Provide a helper which clearly documents the usage of driver_override. This will allow later to reuse the helper and reduce the amount of duplicated code. Convert the platform driver to use a new helper and make the driver_override field const char (it is not modified by the core). Reviewed-by: Rafael J. Wysocki Acked-by: Rafael J. Wysocki Signed-off-by: Krzysztof Kozlowski Link: https://lore.kernel.org/r/20220419113435.246203-2-krzysztof.kozlowski@linaro.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Lee Jones Change-Id: Ib0c76960fce44b52a71e53aa6e30f39e7e8e5175 --- drivers/base/driver.c | 69 +++++++++++++++++++++++++++++++++ drivers/base/platform.c | 28 ++----------- include/linux/device.h | 2 + include/linux/platform_device.h | 6 ++- 4 files changed, 80 insertions(+), 25 deletions(-) diff --git a/drivers/base/driver.c b/drivers/base/driver.c index 4e5ca632f35e8..ef14566a49710 100644 --- a/drivers/base/driver.c +++ b/drivers/base/driver.c @@ -29,6 +29,75 @@ static struct device *next_device(struct klist_iter *i) return dev; } +/** + * driver_set_override() - Helper to set or clear driver override. + * @dev: Device to change + * @override: Address of string to change (e.g. &device->driver_override); + * The contents will be freed and hold newly allocated override. + * @s: NUL-terminated string, new driver name to force a match, pass empty + * string to clear it ("" or "\n", where the latter is only for sysfs + * interface). + * @len: length of @s + * + * Helper to set or clear driver override in a device, intended for the cases + * when the driver_override field is allocated by driver/bus code. + * + * Returns: 0 on success or a negative error code on failure. + */ +int driver_set_override(struct device *dev, const char **override, + const char *s, size_t len) +{ + const char *new, *old; + char *cp; + + if (!override || !s) + return -EINVAL; + + /* + * The stored value will be used in sysfs show callback (sysfs_emit()), + * which has a length limit of PAGE_SIZE and adds a trailing newline. + * Thus we can store one character less to avoid truncation during sysfs + * show. + */ + if (len >= (PAGE_SIZE - 1)) + return -EINVAL; + + if (!len) { + /* Empty string passed - clear override */ + device_lock(dev); + old = *override; + *override = NULL; + device_unlock(dev); + kfree(old); + + return 0; + } + + cp = strnchr(s, len, '\n'); + if (cp) + len = cp - s; + + new = kstrndup(s, len, GFP_KERNEL); + if (!new) + return -ENOMEM; + + device_lock(dev); + old = *override; + if (cp != s) { + *override = new; + } else { + /* "\n" passed - clear override */ + kfree(new); + *override = NULL; + } + device_unlock(dev); + + kfree(old); + + return 0; +} +EXPORT_SYMBOL_GPL(driver_set_override); + /** * driver_for_each_device - Iterator for devices bound to a driver. * @drv: Driver we're iterating. diff --git a/drivers/base/platform.c b/drivers/base/platform.c index 75623b914b8c2..0ed43d185a900 100644 --- a/drivers/base/platform.c +++ b/drivers/base/platform.c @@ -973,31 +973,11 @@ static ssize_t driver_override_store(struct device *dev, const char *buf, size_t count) { struct platform_device *pdev = to_platform_device(dev); - char *driver_override, *old, *cp; - - /* We need to keep extra room for a newline */ - if (count >= (PAGE_SIZE - 1)) - return -EINVAL; - - driver_override = kstrndup(buf, count, GFP_KERNEL); - if (!driver_override) - return -ENOMEM; - - cp = strchr(driver_override, '\n'); - if (cp) - *cp = '\0'; - - device_lock(dev); - old = pdev->driver_override; - if (strlen(driver_override)) { - pdev->driver_override = driver_override; - } else { - kfree(driver_override); - pdev->driver_override = NULL; - } - device_unlock(dev); + int ret; - kfree(old); + ret = driver_set_override(dev, &pdev->driver_override, buf, count); + if (ret) + return ret; return count; } diff --git a/include/linux/device.h b/include/linux/device.h index c7be3a8073ec3..af4ecbf889107 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -422,6 +422,8 @@ extern int __must_check driver_create_file(struct device_driver *driver, extern void driver_remove_file(struct device_driver *driver, const struct driver_attribute *attr); +int driver_set_override(struct device *dev, const char **override, + const char *s, size_t len); extern int __must_check driver_for_each_device(struct device_driver *drv, struct device *start, void *data, diff --git a/include/linux/platform_device.h b/include/linux/platform_device.h index 569f446502bed..c7bd8a1a60976 100644 --- a/include/linux/platform_device.h +++ b/include/linux/platform_device.h @@ -29,7 +29,11 @@ struct platform_device { struct resource *resource; const struct platform_device_id *id_entry; - char *driver_override; /* Driver name to force a match */ + /* + * Driver name to force a match. Do not set directly, because core + * frees it. Use driver_set_override() to set or clear it. + */ + const char *driver_override; /* MFD cell pointer */ struct mfd_cell *mfd_cell; -- 2.42.0.820.g83a721a137-goog