diff mbox series

[v5.15-v5.10,2/4] fs: new helper vfs_empty_path()

Message ID 20240918-statx-stable-linux-5-15-y-v1-2-5afb4401ddbe@gmail.com (mailing list archive)
State New
Headers show
Series Backport statx(..., NULL, AT_EMPTY_PATH, ...) | expand

Commit Message

Miao Wang via B4 Relay Sept. 18, 2024, 2:10 p.m. UTC 
From: Christian Brauner <brauner@kernel.org>

commit 1bc6d44 upstream.

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>

Cc: <stable@vger.kernel.org> # 5.10.x-5.15.x
Signed-off-by: Miao Wang <shankerwangmiao@gmail.com>
Tested-by: Xi Ruoyao <xry111@xry111.site>
---
 include/linux/fs.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
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Patch

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 27da89d0ed5a..6fe2ae89bba6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3736,4 +3736,21 @@  static inline int inode_drain_writes(struct inode *inode)
 	return filemap_write_and_wait(inode->i_mapping);
 }
 
+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 */