smbfs_lookup() in the DOTDOT case operates on dvp->n_parent without

proper locking. This doesn't prevent in any case reclaim of the vnode.
Avoid this not going over-the-wire in this case and relying on subsequent
smbfs_getattr() call to restore consistency.
While I'm here, change a couple of SMBVDEBUG() in MPASS().
sbmfs_smb_lookup() doesn't and shouldn't know about '.' and '..'

Reported by:	pho's stress2 suite

1 files changed, 13 insertions, 6 deletions

diff --git a/sys/fs/smbfs/smbfs_vnops.c b/sys/fs/smbfs/smbfs_vnops.c
index 6285dfd..6ceed9c 100644
--- a/sys/fs/smbfs/smbfs_vnops.c
+++ b/sys/fs/smbfs/smbfs_vnops.c
@@ -1204,13 +1204,20 @@ smbfs_lookup(ap)
 	smb_makescred(scred, td, cnp->cn_cred);
 	fap = &fattr;
 	if (flags & ISDOTDOT) {
-		error = smbfs_smb_lookup(VTOSMB(dnp->n_parent), NULL, 0, fap,
-		    scred);
-		SMBVDEBUG("result of dotdot lookup: %d\n", error);
-	} else {
-		fap = &fattr;
+		/*
+		 * In the DOTDOT case, don't go over-the-wire
+		 * in order to request attributes. We already
+		 * know it's a directory and subsequent call to
+		 * smbfs_getattr() will restore consistency.
+		 *
+		 */
+		SMBVDEBUG("smbfs_smb_lookup: dotdot\n");
+	} else if (isdot) {
+		error = smbfs_smb_lookup(dnp, NULL, 0, fap, scred);
+		SMBVDEBUG("result of smbfs_smb_lookup: %d\n", error);
+	}
+	else {
 		error = smbfs_smb_lookup(dnp, name, nmlen, fap, scred);
-/*		if (cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.')*/
 		SMBVDEBUG("result of smbfs_smb_lookup: %d\n", error);
 	}
 	if (error && error != ENOENT)