From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ED8041EA7DB; Sat, 16 May 2026 14:30:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778941841; cv=none; b=qLSPYtr8/Y+vv7mg+kiAU0Wzhj6oLyvr47vvVijJQANWQVlfOxjk6dtflIbn/wbsKHbQGRyxhAbCnHrG8nijRGU58Kmv7H2fHD2G2/9eLb0BfzMC7Wc9McTOVVuuKgeNrGBtbLW8XRXVkb8CF5Y2RlkPneC1TpKI5qndFnNKVsY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778941841; c=relaxed/simple; bh=+VmfiZN2bHst+5NOjkKuH+N2dM9CR9Nbis0U7S/zB+A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GSYMEQmvDap/sOqKZr07OdwMHMQgmZKEbH32DTrkaUn14VsigmUFRv92xif53VZqKCM93zfrpqf7Fy6kqI6u/1XtiGBeAJnnv8k8VvAxdX6EzX9Xu4d0fEr100A2FcD7u62iQJET/N2f7btvAZEyN0m1a/oZXnXYI99Kh4atw6w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qB5ABzTi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qB5ABzTi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40AF6C2BCC9; Sat, 16 May 2026 14:30:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778941838; bh=+VmfiZN2bHst+5NOjkKuH+N2dM9CR9Nbis0U7S/zB+A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qB5ABzTiFPNrlzt/Oj1uoouvvVQdPGyK1kYJEwbYBm0ZBabz2am3GU35k11uFVAZV Qxy0mHUyPd70SOAaJGlB72XSQkQC7MOiKm0ELi4dIJ7uKqOGX7qsuYEeXB9U205BSb wrwx237QL95jX5ps0oAftLMDr7z5HIIv+0wbM4N5eeu2R3UkI3fnNZF/TZJEXJcg7O HsJkjWwNz7x3/GUMujjinw/fErMNX1DXXPIZrmxY5rJFdfWkoL4o/BJdod5PsWlfvv u4oFRUi2wkTs2VzggrL6Ae1BMc0fNKrrv0fClf8vX91tZcv8PpCvjWVq6iO0D958LF /WTysOvgJF/Vg== From: Tzung-Bi Shih To: Benson Leung , Jason Gunthorpe , Greg Kroah-Hartman Cc: tzungbi@kernel.org, chrome-platform@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH v2 4/4] platform/chrome: cros_ec_chardev: Introduce rwsem for protecting ec_dev Date: Sat, 16 May 2026 22:30:17 +0800 Message-ID: <20260516143017.18560-5-tzungbi@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260516143017.18560-1-tzungbi@kernel.org> References: <20260516143017.18560-1-tzungbi@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce a rwsem for protecting `ec_dev` to prevent Use-After-Free on the `ec_dev`. - Writers: In driver's probe() and remove(). - Readers: In file operations. Signed-off-by: Tzung-Bi Shih --- v2: - New to the series. v1: Doesn't exist. drivers/platform/chrome/cros_ec_chardev.c | 68 +++++++++++++++++------ 1 file changed, 52 insertions(+), 16 deletions(-) diff --git a/drivers/platform/chrome/cros_ec_chardev.c b/drivers/platform/chrome/cros_ec_chardev.c index 7e046fc56998..450f79759122 100644 --- a/drivers/platform/chrome/cros_ec_chardev.c +++ b/drivers/platform/chrome/cros_ec_chardev.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -38,6 +39,7 @@ struct chardev_pdata { struct miscdevice misc; struct kref kref; + struct rw_semaphore ec_dev_sem; struct cros_ec_device *ec_dev; u16 cmd_offset; struct blocking_notifier_head subscribers; @@ -94,12 +96,19 @@ static int ec_get_version(struct chardev_priv *priv, char *str, int maxlen) msg->command = EC_CMD_GET_VERSION + priv->pdata->cmd_offset; msg->insize = sizeof(*resp); - ret = cros_ec_cmd_xfer_status(priv->pdata->ec_dev, msg); - if (ret < 0) { - snprintf(str, maxlen, - "Unknown EC version, returned error: %d\n", - msg->result); - goto exit; + scoped_guard(rwsem_read, &priv->pdata->ec_dev_sem) { + if (!priv->pdata->ec_dev) { + ret = -ENODEV; + goto exit; + } + + ret = cros_ec_cmd_xfer_status(priv->pdata->ec_dev, msg); + if (ret < 0) { + snprintf(str, maxlen, + "Unknown EC version, returned error: %d\n", + msg->result); + goto exit; + } } resp = (struct ec_response_get_version *)msg->data; @@ -122,10 +131,18 @@ static int cros_ec_chardev_mkbp_event(struct notifier_block *nb, { struct chardev_priv *priv = container_of(nb, struct chardev_priv, notifier); - struct cros_ec_device *ec_dev = priv->pdata->ec_dev; + struct cros_ec_device *ec_dev; struct ec_event *event; - unsigned long event_bit = 1 << ec_dev->event_data.event_type; - int total_size = sizeof(*event) + ec_dev->event_size; + unsigned long event_bit; + int total_size; + + guard(rwsem_read)(&priv->pdata->ec_dev_sem); + if (!priv->pdata->ec_dev) + return NOTIFY_DONE; + ec_dev = priv->pdata->ec_dev; + + event_bit = 1 << ec_dev->event_data.event_type; + total_size = sizeof(*event) + ec_dev->event_size; if (!(event_bit & priv->event_mask) || (priv->event_len + total_size) > CROS_MAX_EVENT_LEN) @@ -206,8 +223,11 @@ static int cros_ec_chardev_open(struct inode *inode, struct file *filp) ret = blocking_notifier_chain_register(&pdata->subscribers, &priv->notifier); if (ret) { - dev_err(pdata->ec_dev->dev, - "failed to register event notifier\n"); + scoped_guard(rwsem_read, &pdata->ec_dev_sem) { + if (pdata->ec_dev) + dev_err(pdata->ec_dev->dev, + "failed to register event notifier\n"); + } kref_put(&priv->pdata->kref, chardev_pdata_release); kfree(priv); } @@ -330,10 +350,18 @@ static long cros_ec_chardev_ioctl_xcmd(struct chardev_priv *priv, void __user *a } s_cmd->command += priv->pdata->cmd_offset; - ret = cros_ec_cmd_xfer(priv->pdata->ec_dev, s_cmd); - /* Only copy data to userland if data was received. */ - if (ret < 0) - goto exit; + + scoped_guard(rwsem_read, &priv->pdata->ec_dev_sem) { + if (!priv->pdata->ec_dev) { + ret = -ENODEV; + goto exit; + } + + ret = cros_ec_cmd_xfer(priv->pdata->ec_dev, s_cmd); + /* Only copy data to userland if data was received. */ + if (ret < 0) + goto exit; + } if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize)) ret = -EFAULT; @@ -344,10 +372,15 @@ static long cros_ec_chardev_ioctl_xcmd(struct chardev_priv *priv, void __user *a static long cros_ec_chardev_ioctl_readmem(struct chardev_priv *priv, void __user *arg) { - struct cros_ec_device *ec_dev = priv->pdata->ec_dev; + struct cros_ec_device *ec_dev; struct cros_ec_readmem s_mem = { }; long num; + guard(rwsem_read)(&priv->pdata->ec_dev_sem); + if (!priv->pdata->ec_dev) + return -ENODEV; + ec_dev = priv->pdata->ec_dev; + /* Not every platform supports direct reads */ if (!ec_dev->cmd_readmem) return -ENOTTY; @@ -414,6 +447,7 @@ static int cros_ec_chardev_probe(struct platform_device *pdev) platform_set_drvdata(pdev, pdata); kref_init(&pdata->kref); + init_rwsem(&pdata->ec_dev_sem); pdata->ec_dev = ec->ec_dev; pdata->cmd_offset = ec->cmd_offset; BLOCKING_INIT_NOTIFIER_HEAD(&pdata->subscribers); @@ -451,6 +485,8 @@ static void cros_ec_chardev_remove(struct platform_device *pdev) blocking_notifier_chain_unregister(&pdata->ec_dev->event_notifier, &pdata->relay); + scoped_guard(rwsem_write, &pdata->ec_dev_sem) + pdata->ec_dev = NULL; misc_deregister(&pdata->misc); kref_put(&pdata->kref, chardev_pdata_release); } -- 2.51.0