[PATCH] fcntl fix

[Andries.Brouwer@cwi.nl]

People asked me to document that Linux has a non-POSIX-compliant
fcntl system call. Maybe fixing fcntl is better.
No doubt the same patch should be applied to 2.2 and 2.4,
but let's do 2.5 first.

--- /linux/2.5/linux-2.5.18/linux/fs/locks.c	Tue May 21 07:07:37 2002
+++ /linux/2.5/linux-2.5.18a/linux/fs/locks.c	Mon May 27 17:25:33 2002
@@ -274,9 +274,18 @@
 		return -EINVAL;
 	}
 
-	if (((start += l->l_start) < 0) || (l->l_len < 0))
+	/* POSIX-1996 leaves the case l->l_len < 0 undefined;
+	   POSIX-2001 defines it. */
+	start += l->l_start;
+	if (l->l_len < 0) {
+		end = start - 1;
+		start += l->l_len;
+	} else {
+		end = start + l->l_len - 1;
+	}
+
+	if (start < 0)
 		return -EINVAL;
-	end = start + l->l_len - 1;
 	if (l->l_len > 0 && end < 0)
 		return -EOVERFLOW;
 	fl->fl_start = start;	/* we record the absolute position */

Andries