[PATCH] stat nlink resolution fix

Some filesystems can get overflows when their link-count exceeds
65534.  This patch increases the kernels internal resolution for this
and also has a check for the old-system call paths to return and error
(-EOVERFLOW) as required (as suggested by Al Viro).
Signed-off-by: Chris Wedgwood <cw@f00f.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/stat.c

@@ -131,6 +131,8 @@ static int cp_old_stat(struct kstat *stat, struct __old_kernel_stat __user * sta
 	tmp.st_ino = stat->ino;
 	tmp.st_mode = stat->mode;
 	tmp.st_nlink = stat->nlink;
+	if (tmp.st_nlink != stat->nlink)
+		return -EOVERFLOW;
 	SET_UID(tmp.st_uid, stat->uid);
 	SET_GID(tmp.st_gid, stat->gid);
 	tmp.st_rdev = old_encode_dev(stat->rdev);
@@ -199,6 +201,8 @@ static int cp_new_stat(struct kstat *stat, struct stat __user *statbuf)
 	tmp.st_ino = stat->ino;
 	tmp.st_mode = stat->mode;
 	tmp.st_nlink = stat->nlink;
+	if (tmp.st_nlink != stat->nlink)
+		return -EOVERFLOW;
 	SET_UID(tmp.st_uid, stat->uid);
 	SET_GID(tmp.st_gid, stat->gid);
 #if BITS_PER_LONG == 32

include/linux/stat.h

@@ -60,7 +60,7 @@ struct kstat {
 	unsigned long	ino;
 	dev_t		dev;
 	umode_t		mode;
-	nlink_t		nlink;
+	unsigned int	nlink;
 	uid_t		uid;
 	gid_t		gid;
 	dev_t		rdev;