[PATCH man-pages 3/3] open.2: describe O_BENEATH flag

@@ -716,6 +716,31 @@ XFS support was added
 .\" commit ab29743117f9f4c22ac44c13c1647fb24fb2bafe
 in Linux 3.15.
 .TP
+.B O_BENEATH " (since Linux 3.??)"
+Ensure that the
+.I pathname
+is beneath the current working directory (for
+.BR open (2))
+or the
+.I dirfd
+(for
+.BR openat (2)).
+If the
+.I pathname
+is absolute or contains a path component of "..", the
+.BR open ()
+fails with the error
+.BR EACCES.
+This occurs even if ".." path component would not actually
+escape the original directory; for example, a
+.I pathname
+of "subdir/../filename" would be rejected.
+Path components that are symbolic links to absolute paths, or that are
+relative paths containing a ".." component, will also cause the
+.BR open ()
+operation to fail with the error
+.BR EACCES.
+.TP
 .B O_TRUNC
 If the file already exists and is a regular file and the access mode allows
 writing (i.e., is

@@ -792,7 +817,11 @@ The requested access to the file is not allowed, or search permission
 is denied for one of the directories in the path prefix of
 .IR pathname ,
 or the file did not exist yet and write access to the parent directory
-is not allowed.
+is not allowed, or the
+.B O_BENEATH
+flag was specified and the
+.I pathname
+was not beneath the relevant directory.
 (See also
 .BR path_resolution (7).)
 .TP