linux-kernel - [PATCH v8 1/9] libfs: Create the helper function generic_ci_validate_strict

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Message-Id: <20241021-tonyk-tmpfs-v8-1-f443d5814194@igalia.com>
Date: Mon, 21 Oct 2024 13:37:17 -0300
From: André Almeida <andrealmeid@...lia.com>
To: Gabriel Krisman Bertazi <krisman@...nel.org>, 
 Alexander Viro <viro@...iv.linux.org.uk>, 
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
 Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, 
 Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
 Jonathan Corbet <corbet@....net>, smcv@...labora.com
Cc: kernel-dev@...lia.com, linux-fsdevel@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org, 
 linux-mm@...ck.org, linux-doc@...r.kernel.org, 
 Gabriel Krisman Bertazi <krisman@...e.de>, 
 Gabriel Krisman Bertazi <gabriel@...sman.be>, 
 André Almeida <andrealmeid@...lia.com>
Subject: [PATCH v8 1/9] libfs: Create the helper function
 generic_ci_validate_strict_name()

Create a helper function for filesystems do the checks required for
casefold directories and strict encoding.

Suggested-by: Gabriel Krisman Bertazi <krisman@...e.de>
Reviewed-by: Gabriel Krisman Bertazi <gabriel@...sman.be>
Signed-off-by: André Almeida <andrealmeid@...lia.com>
---
Changes from v6:
- Correctly negate utf8_validate() return

Changes from v4:
- Inline this function

Changes from v2:
- Moved function to libfs and adpated its name
- Wrapped at 72 chars column
- Decomposed the big if (...) to be more clear
---
 include/linux/fs.h | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3559446279c152c70b7f1f3e0154f6e66a5aba33..403ee5d54c60a0a97e2eba9ef80d8fb4bbd2288f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -45,6 +45,7 @@
 #include <linux/slab.h>
 #include <linux/maple_tree.h>
 #include <linux/rw_hint.h>
+#include <linux/unicode.h>
 
 #include <asm/byteorder.h>
 #include <uapi/linux/fs.h>
@@ -3456,6 +3457,50 @@ extern int generic_ci_match(const struct inode *parent,
 			    const struct qstr *folded_name,
 			    const u8 *de_name, u32 de_name_len);
 
+#if IS_ENABLED(CONFIG_UNICODE)
+/**
+ * generic_ci_validate_strict_name - Check if a given name is suitable
+ * for a directory
+ *
+ * This functions checks if the proposed filename is valid for the
+ * parent directory. That means that only valid UTF-8 filenames will be
+ * accepted for casefold directories from filesystems created with the
+ * strict encoding flag.  That also means that any name will be
+ * accepted for directories that doesn't have casefold enabled, or
+ * aren't being strict with the encoding.
+ *
+ * @dir: inode of the directory where the new file will be created
+ * @name: name of the new file
+ *
+ * Return:
+ * * True if the filename is suitable for this directory. It can be
+ * true if a given name is not suitable for a strict encoding
+ * directory, but the directory being used isn't strict
+ * * False if the filename isn't suitable for this directory. This only
+ * happens when a directory is casefolded and the filesystem is strict
+ * about its encoding.
+ */
+static inline bool generic_ci_validate_strict_name(struct inode *dir, struct qstr *name)
+{
+	if (!IS_CASEFOLDED(dir) || !sb_has_strict_encoding(dir->i_sb))
+		return true;
+
+	/*
+	 * A casefold dir must have a encoding set, unless the filesystem
+	 * is corrupted
+	 */
+	if (WARN_ON_ONCE(!dir->i_sb->s_encoding))
+		return true;
+
+	return !utf8_validate(dir->i_sb->s_encoding, name);
+}
+#else
+static inline bool generic_ci_validate_strict_name(struct inode *dir, struct qstr *name)
+{
+	return true;
+}
+#endif
+
 static inline bool sb_has_encoding(const struct super_block *sb)
 {
 #if IS_ENABLED(CONFIG_UNICODE)

-- 
2.47.0