From: Christian Brauner <brauner@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 6.6.x
Signed-off-by: Miao Wang <shankerwangmiao@xxxxxxxxx>
Tested-by: Xi Ruoyao <xry111@xxxxxxxxxxx>
---
include/linux/fs.h | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2a554e4045a9..809b354dbddf 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3454,4 +3454,21 @@ 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 */
--
2.43.0
