From: Christian Brauner <brauner@kernel.org>
Date: Tue, 30 Apr 2024 11:54:46 +0000 (+0200)
Subject: fs: new helper vfs_empty_path()
X-Git-Tag: v6.11-rc1~242^2~4
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1bc6d4452d5c91beb09e37a98a590808e1997b79;p=thirdparty%2Fkernel%2Flinux.git

fs: new helper vfs_empty_path()

Make it possible to quickly check whether AT_EMPTY_PATH is valid.
Note, after some discussion we decided to also allow NULL to be passed
instead of requiring the empty string.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 942cb11dba961..5ff362277834c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3631,4 +3631,21 @@ extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,
 extern int generic_fadvise(struct file *file, loff_t offset, loff_t len,
 			   int advice);
 
+static inline bool vfs_empty_path(int dfd, const char __user *path)
+{
+	char c;
+
+	if (dfd < 0)
+		return false;
+
+	/* We now allow NULL to be used for empty path. */
+	if (!path)
+		return true;
+
+	if (unlikely(get_user(c, path)))
+		return false;
+
+	return !c;
+}
+
 #endif /* _LINUX_FS_H */