Move the truncation code out of vn_open and into the open system call

after the acquisition of any advisory locks. This fix corrects a case
in which a process tries to open a file with a non-blocking exclusive
lock. Even if it fails to get the lock it would still truncate the
file even though its open failed. With this change, the truncation
is done only after the lock is successfully acquired.

Obtained from:	 BSD/OS

1 files changed, 13 insertions, 24 deletions

diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 9dedcbe2c2b4..0d0dc24dc574 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -98,25 +98,25 @@ struct filterops vn_rwfiltops[] = {
  * due to the NDINIT being done elsewhere.
  */
 int
-vn_open(ndp, fmode, cmode)
+vn_open(ndp, flagp, cmode)
 	register struct nameidata *ndp;
-	int fmode, cmode;
+	int *flagp, cmode;
 {
-	register struct vnode *vp;
-	register struct proc *p = ndp->ni_cnd.cn_proc;
-	register struct ucred *cred = p->p_ucred;
+	struct vnode *vp;
+	struct proc *p = ndp->ni_cnd.cn_proc;
+	struct ucred *cred = p->p_ucred;
 	struct vattr vat;
 	struct vattr *vap = &vat;
-	int mode, error;
+	int mode, fmode, error;
 
+	fmode = *flagp;
 	if (fmode & O_CREAT) {
 		ndp->ni_cnd.cn_nameiop = CREATE;
 		ndp->ni_cnd.cn_flags = LOCKPARENT | LOCKLEAF;
 		if ((fmode & O_EXCL) == 0 && (fmode & O_NOFOLLOW) == 0)
 			ndp->ni_cnd.cn_flags |= FOLLOW;
 		bwillwrite();
-		error = namei(ndp);
-		if (error)
+		if ((error = namei(ndp)) != 0)
 			return (error);
 		if (ndp->ni_vp == NULL) {
 			VATTR_NULL(vap);
@@ -127,12 +127,11 @@ vn_open(ndp, fmode, cmode)
 			VOP_LEASE(ndp->ni_dvp, p, cred, LEASE_WRITE);
 			error = VOP_CREATE(ndp->ni_dvp, &ndp->ni_vp,
 					   &ndp->ni_cnd, vap);
+			vput(ndp->ni_dvp);
 			if (error) {
 				NDFREE(ndp, NDF_ONLY_PNBUF);
-				vput(ndp->ni_dvp);
 				return (error);
 			}
-			vput(ndp->ni_dvp);
 			ASSERT_VOP_UNLOCKED(ndp->ni_dvp, "create");
 			ASSERT_VOP_LOCKED(ndp->ni_vp, "create");
 			fmode &= ~O_TRUNC;
@@ -154,8 +153,7 @@ vn_open(ndp, fmode, cmode)
 		ndp->ni_cnd.cn_nameiop = LOOKUP;
 		ndp->ni_cnd.cn_flags =
 		    ((fmode & O_NOFOLLOW) ? NOFOLLOW : FOLLOW) | LOCKLEAF;
-		error = namei(ndp);
-		if (error)
+		if ((error = namei(ndp)) != 0)
 			return (error);
 		vp = ndp->ni_vp;
 	}
@@ -187,18 +185,7 @@ vn_open(ndp, fmode, cmode)
 				goto bad;
 		}
 	}
-	if (fmode & O_TRUNC) {
-		VOP_UNLOCK(vp, 0, p);				/* XXX */
-		VOP_LEASE(vp, p, cred, LEASE_WRITE);
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);	/* XXX */
-		VATTR_NULL(vap);
-		vap->va_size = 0;
-		error = VOP_SETATTR(vp, vap, cred, p);
-		if (error)
-			goto bad;
-	}
-	error = VOP_OPEN(vp, fmode, cred, p);
-	if (error)
+	if ((error = VOP_OPEN(vp, fmode, cred, p)) != 0)
 		goto bad;
 	/*
 	 * Make sure that a VM object is created for VMIO support.
@@ -210,10 +197,12 @@ vn_open(ndp, fmode, cmode)
 
 	if (fmode & FWRITE)
 		vp->v_writecount++;
+	*flagp = fmode;
 	return (0);
 bad:
 	NDFREE(ndp, NDF_ONLY_PNBUF);
 	vput(vp);
+	*flagp = fmode;
 	return (error);
 }