From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpbgeu1.qq.com (smtpbgeu1.qq.com [52.59.177.22]) (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 4961441F5C8; Thu, 6 Aug 2026 08:49:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.59.177.22 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786006164; cv=none; b=fXejqh37ohU6OXT1WI56OlIGdDON+ngUuEQe9jLh6GjOGAgpEWsERZq372xBdcBsxQZBrJH7YdBoCQzrDLBr5kmk3lE8cY5B1nWaa1QbQ41cn1wal/DoChxtrHWxmm9+RVtCtdZB+TMyxDodOzeA8OuZshZRIiRlCX2a0C/bUgA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786006164; c=relaxed/simple; bh=ePp+RxiutBCyzzEvl5K1dmKuPb/y40CYrZgkRG5vNg0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=CzkBfx2wdontdI+UpzbdJla4eDqtYTQabnkAmKaRNdvYDmahu51z0CEUe5ZnZvMb7sacJPzYsGCiOKLyxfVeiwSvEVXaL5RGXdQgGspSMl+dUJBIZHuUS8AU2CbI5j8PBlA4Hn1uoI5FQOrlqSqYyg48AnLX9PJ2USB9IEq8fSo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=uniontech.com; spf=pass smtp.mailfrom=uniontech.com; dkim=pass (1024-bit key) header.d=uniontech.com header.i=@uniontech.com header.b=LqbrOUy2; arc=none smtp.client-ip=52.59.177.22 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=uniontech.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=uniontech.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=uniontech.com header.i=@uniontech.com header.b="LqbrOUy2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=uniontech.com; s=onoh2408; t=1786006157; bh=qvo8GnxR4HBw5KUhU+lgGsArbxbsBLDwyjUKHDJAdeY=; h=From:To:Subject:Date:Message-Id:MIME-Version; b=LqbrOUy2TqqM0OtmFMg1/aUcsufALMPN0WLPugFfgvfYGAHSNMdnqjCmqaW3ywnan bZw8xMgQnOX7SEuRn+bmzVftjP7xDhZgBnh7uMlZK4bB2w+2UJZlqYf+PDSrfrr54Z 85fsL5X+JGjQKvsIwLyuqnSuS2vG4cKgjQ9Y7a7Q= X-QQ-mid: esmtpgz10t1786006153t5a193209 X-QQ-Originating-IP: JVhbFHdaKldKfaSuDbI31KdscLgt26kiGyz/MsQ1sFk= Received: from uniontech.com ( [113.57.152.160]) by bizesmtp.qq.com (ESMTP) with id ; Thu, 06 Aug 2026 16:49:10 +0800 (CST) X-QQ-SSF: 0000000000000000000000000000000 X-QQ-GoodBg: 1 X-BIZMAIL-ID: 11587436272673348081 EX-QQ-RecipientCnt: 13 From: Yichong Chen To: gregkh@linuxfoundation.org Cc: rafael@kernel.org, dakr@kernel.org, djakov@kernel.org, quic_mdtipton@quicinc.com, vkoul@kernel.org, yung-chuan.liao@linux.intel.com, pierre-louis.bossart@linux.dev, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-sound@vger.kernel.org, Yichong Chen Subject: [PATCH v2 3/3] debugfs: make debugfs_create_str() read-only Date: Thu, 6 Aug 2026 16:48:54 +0800 Message-Id: <20260806084854.1019789-4-chenyichong@uniontech.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20260806084854.1019789-1-chenyichong@uniontech.com> References: <20260806084854.1019789-1-chenyichong@uniontech.com> Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-QQ-SENDSIZE: 520 Feedback-ID: esmtpgz:uniontech.com:qybglogicsvrgz:qybglogicsvrgz3a-0 X-QQ-XMAILINFO: Mh1JMxfliF/1MGldjCRDRJRwJtAVKKQlCrJHxteiApDdMbhGrm5tquH/ Xv2XAbGoAvGCCXOWJHRwTVf/YfbF/FmeNzF5WC6Yr43wkBJUXlgR9/iUAK/uAtBeGQsWr9m wdGWkW0aq3DId0HWZvyWUeqhC1XdDugPtOsqSamTb7KjXlY1hMUCXWtSoJxss8eYTmuxdfq GsKdXDCVXmssOi84PBSKMkBHrN6/FwMUny0sKWt6nAYr5lDQV5A1wzxeqSZcqaFiMbDCNTz gwZfIf7qnIsH7NsQpUd/tdSjetbmHo5hZvsxvDnfijhsMBhz09H5IQw5DeurlRt45woT2l3 0qKBQxJXL510ZFk9OqvMW8qTTltzcPNKTVlZxJv9wPvRR8EjnVC4ImyyfWXRFxeq8ZvQDNK OxTIPptbGPzKBaObMMiAQJVAi8AQC/ori1i5raCkp+OFaX1P1+PyiIRfDnfb85Y2jUWJe73 tHOxPqoieiD0qCqPRVsIvYnYiiBbwaCTIe+SAMI0oRAX28Ong0K/LuaUTL8KYOLXpHWZNZA s+FQZseN0ZXVZdz93IlLKH0vUg8QmII6iUl7EvMeZruTtS4qpDZ0P2gCuqobCEztG61hpum vPg6Dv6LpTOPF7eCRULC0HU846i5tK6LlTnXpFHEiTs9WhBZqvfScb/i3/AUK5s/Eg10B2e 7l3uHbFuPs3WZqvelvKMf/UwoefKHQJYuhaV6MLvVT7si5jNVlTiC+HXWALSWjV8dPSEhdZ DXWeLqTmVhWkG/2VX+fErGB/EYo4rc4D/4ApKMsZ5Mz1dkHSl9bVR49xQC5UJzcu+MUGywq sh8XwyreqvfFDmAtEixuq2TXZg9HBLZ8VTTyN+bcLHh6dLPLkEP/N0r3NkqBC1w3cW35Bil y0ZYA1/O6zhuDAaBu6OquWo8YzfRJrn581IA1VOOfWfgAkVSTZSVQsnNmiGiBpKVO71ZrwE vxxSUItxROxg766dTOQJCJ9T9oIcGVcrFRbL034EyWmHz0CWvLIN0RzmUys5esdHAx4gp2l xL1Qrgwjgg4XPCnPzjfycGHMnXfPwM2b0sAZm6HRT0OBMgBU+r6hn/QS5dWWU= X-QQ-XMRINFO: MSVp+SPm3vtSI1QTLgDHQqIV1w2oNKDqfg== X-QQ-RECHKSPAM: 0 debugfs_create_str() supports replacing the backing string from userspace. Concurrent writers can race and free the same old string twice. All writable in-tree users have been converted to local file operations. Remove the generic write support from debugfs_create_str(), and refuse to create a file when the caller passes write permission bits. This makes unsupported writable use visible instead of silently creating a file with different permissions. Fixes: 86b5488121db ("debugfs: Add write support to debugfs_create_str()") Signed-off-by: Yichong Chen --- fs/debugfs/file.c | 81 ++++++----------------------------------------- 1 file changed, 10 insertions(+), 71 deletions(-) diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index 08de6652a4f3..f5abd067b260 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -1049,98 +1049,37 @@ ssize_t debugfs_read_file_str(struct file *file, char __user *user_buf, return ret; } -static ssize_t debugfs_write_file_str(struct file *file, const char __user *user_buf, - size_t count, loff_t *ppos) -{ - struct dentry *dentry = F_DENTRY(file); - char *old, *new = NULL; - int pos = *ppos; - int r; - - r = debugfs_file_get(dentry); - if (unlikely(r)) - return r; - - old = *(char **)file->private_data; - - /* only allow strict concatenation */ - r = -EINVAL; - if (pos && pos != strlen(old)) - goto error; - - r = -E2BIG; - if (pos + count + 1 > PAGE_SIZE) - goto error; - - r = -ENOMEM; - new = kmalloc(pos + count + 1, GFP_KERNEL); - if (!new) - goto error; - - if (pos) - memcpy(new, old, pos); - - r = -EFAULT; - if (copy_from_user(new + pos, user_buf, count)) - goto error; - - new[pos + count] = '\0'; - strim(new); - - rcu_assign_pointer(*(char __rcu **)file->private_data, new); - synchronize_rcu(); - kfree(old); - - debugfs_file_put(dentry); - return count; - -error: - kfree(new); - debugfs_file_put(dentry); - return r; -} - static const struct file_operations fops_str = { .read = debugfs_read_file_str, - .write = debugfs_write_file_str, - .open = simple_open, - .llseek = default_llseek, -}; - -static const struct file_operations fops_str_ro = { - .read = debugfs_read_file_str, - .open = simple_open, - .llseek = default_llseek, -}; - -static const struct file_operations fops_str_wo = { - .write = debugfs_write_file_str, .open = simple_open, .llseek = default_llseek, }; /** - * debugfs_create_str - create a debugfs file that is used to read and write a string value + * debugfs_create_str - create a debugfs file that is used to read a string value * @name: a pointer to a string containing the name of the file to create. * @mode: the permission that the file should have * @parent: a pointer to the parent dentry for this file. This should be a * directory dentry if set. If this parameter is %NULL, then the * file will be created in the root of the debugfs filesystem. - * @value: a pointer to the variable that the file should read to and write - * from. This pointer and the string it points to must not be %NULL. + * @value: a pointer to the variable that the file should read from. This + * pointer and the string it points to must not be %NULL. * * This function creates a file in debugfs with the given name that - * contains the value of the variable @value. If the @mode variable is so - * set, it can be read from, and written to. + * contains the value of the variable @value. The file can be read from. + * Writable files are not supported; if @mode contains write permission bits, + * no file is created. */ void debugfs_create_str(const char *name, umode_t mode, struct dentry *parent, char **value) { if (WARN_ON(!value || !*value)) return; + if (WARN_ONCE(mode & 0222, + "%s() does not support writable files\n", __func__)) + return; - debugfs_create_mode_unsafe(name, mode, parent, value, &fops_str, - &fops_str_ro, &fops_str_wo); + debugfs_create_file_unsafe(name, mode, parent, value, &fops_str); } EXPORT_SYMBOL_GPL(debugfs_create_str); -- 2.51.0