Module Name: src
Committed By: dholland
Date: Sun Jun 16 00:13:58 UTC 2013
Modified Files:
src/sys/ufs/ufs: ufs_vnops.c
Log Message:
Add a comment about a matched pair of off-by-one tests that make the
maximum size of short symlinks one byte less than one would think it
should be. Caution against changing it; that would break compatibility
with existing disk images. Behavior noticed by qjsgkem on freenode.
If my analysis is wrong, please correct...
To generate a diff of this commit:
cvs rdiff -u -r1.215 -r1.216 src/sys/ufs/ufs/ufs_vnops.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/ufs/ufs/ufs_vnops.c
diff -u src/sys/ufs/ufs/ufs_vnops.c:1.215 src/sys/ufs/ufs/ufs_vnops.c:1.216
--- src/sys/ufs/ufs/ufs_vnops.c:1.215 Sun Jun 9 18:54:05 2013
+++ src/sys/ufs/ufs/ufs_vnops.c Sun Jun 16 00:13:58 2013
@@ -1,4 +1,4 @@
-/* $NetBSD: ufs_vnops.c,v 1.215 2013/06/09 18:54:05 christos Exp $ */
+/* $NetBSD: ufs_vnops.c,v 1.216 2013/06/16 00:13:58 dholland Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -66,7 +66,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ufs_vnops.c,v 1.215 2013/06/09 18:54:05 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ufs_vnops.c,v 1.216 2013/06/16 00:13:58 dholland Exp $");
#if defined(_KERNEL_OPT)
#include "opt_ffs.h"
@@ -1267,6 +1267,13 @@ ufs_symlink(void *v)
vp = *vpp;
len = strlen(ap->a_target);
ip = VTOI(vp);
+ /*
+ * This test is off by one. um_maxsymlinklen contains the
+ * number of bytes available, and we aren't storing a \0, so
+ * the test should properly be <=. However, it cannot be
+ * changed as this would break compatibility with existing fs
+ * images -- see the way ufs_readlink() works.
+ */
if (len < ip->i_ump->um_maxsymlinklen) {
memcpy((char *)SHORTLINK(ip), ap->a_target, len);
ip->i_size = len;
@@ -1453,6 +1460,12 @@ ufs_readlink(void *v)
struct ufsmount *ump = VFSTOUFS(vp->v_mount);
int isize;
+ /*
+ * The test against um_maxsymlinklen is off by one; it should
+ * theoretically be <=, not <. However, it cannot be changed
+ * as that would break compatibility with existing fs images.
+ */
+
isize = ip->i_size;
if (isize < ump->um_maxsymlinklen ||
(ump->um_maxsymlinklen == 0 && DIP(ip, blocks) == 0)) {
