Initialize va_filerev in vattr_null() to avoid leaking stack garbage;

problem pointed out by Martin Natano (natano (at) natano.net)

Also, stop chaining assignments (foo = bar = baz) in vattr_null().
The exact meaning of those depends on the order of the sizes-and-
signednesses of the lvalues, making them fragile: a statement here
mixed *six* types, but managed to get them in a safe order.  Delete
a 20+ year old XXX comment that was almost certainly bemoaning a bug
from when they were in an unsafe order.

ok deraadt@ miod@

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 3e19fe5..a78a8ae 100644 (file)
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: vfs_subr.c,v 1.235 2015/10/08 08:41:58 mpi Exp $      */
+/*     $OpenBSD: vfs_subr.c,v 1.236 2015/10/13 09:11:48 guenther Exp $ */
 /*     $NetBSD: vfs_subr.c,v 1.53 1996/04/22 01:39:13 christos Exp $   */
 
 /*
@@ -296,16 +296,30 @@ vattr_null(struct vattr *vap)
 {
 
        vap->va_type = VNON;
-       /* XXX These next two used to be one line, but for a GCC bug. */
+       /*
+        * Don't get fancy: u_quad_t = u_int = VNOVAL leaves the u_quad_t
+        * with 2^31-1 instead of 2^64-1.  Just write'm out and let
+        * the compiler do its job.
+        */
+       vap->va_mode = VNOVAL;
+       vap->va_nlink = VNOVAL;
+       vap->va_uid = VNOVAL;
+       vap->va_gid = VNOVAL;
+       vap->va_fsid = VNOVAL;
+       vap->va_fileid = VNOVAL;
        vap->va_size = VNOVAL;
+       vap->va_blocksize = VNOVAL;
+       vap->va_atime.tv_sec = VNOVAL;
+       vap->va_atime.tv_nsec = VNOVAL;
+       vap->va_mtime.tv_sec = VNOVAL;
+       vap->va_mtime.tv_nsec = VNOVAL;
+       vap->va_ctime.tv_sec = VNOVAL;
+       vap->va_ctime.tv_nsec = VNOVAL;
+       vap->va_gen = VNOVAL;
+       vap->va_flags = VNOVAL;
+       vap->va_rdev = VNOVAL;
        vap->va_bytes = VNOVAL;
-       vap->va_mode = vap->va_nlink = vap->va_uid = vap->va_gid =
-               vap->va_fsid = vap->va_fileid =
-               vap->va_blocksize = vap->va_rdev =
-               vap->va_atime.tv_sec = vap->va_atime.tv_nsec =
-               vap->va_mtime.tv_sec = vap->va_mtime.tv_nsec =
-               vap->va_ctime.tv_sec = vap->va_ctime.tv_nsec =
-               vap->va_flags = vap->va_gen = VNOVAL;
+       vap->va_filerev = VNOVAL;
        vap->va_vaflags = 0;
 }