1 files changed, 47 insertions, 0 deletions
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 05d9de5..cee1f2a 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -4253,3 +4253,50 @@ vfs_mark_atime(struct vnode *vp, struct ucred *cred)
 	if ((vp->v_mount->mnt_flag & (MNT_NOATIME | MNT_RDONLY)) == 0)
 		(void)VOP_MARKATIME(vp);
 }
+
+/*
+ * The purpose of this routine is to remove granularity from accmode_t,
+ * reducing it into standard unix access bits - VEXEC, VREAD, VWRITE,
+ * VADMIN and VAPPEND.
+ *
+ * If it returns 0, the caller is supposed to continue with the usual
+ * access checks using 'accmode' as modified by this routine.  If it
+ * returns nonzero value, the caller is supposed to return that value
+ * as errno.
+ *
+ * Note that after this routine runs, accmode may be zero.
+ */
+int
+vfs_unixify_accmode(accmode_t *accmode)
+{
+	/*
+	 * There is no way to specify explicit "deny" rule using
+	 * file mode or POSIX.1e ACLs.
+	 */
+	if (*accmode & VEXPLICIT_DENY) {
+		*accmode = 0;
+		return (0);
+	}
+
+	/*
+	 * None of these can be translated into usual access bits.
+	 * Also, the common case for NFSv4 ACLs is to not contain
+	 * either of these bits. Caller should check for VWRITE
+	 * on the containing directory instead.
+	 */
+	if (*accmode & (VDELETE_CHILD | VDELETE))
+		return (EPERM);
+
+	if (*accmode & VADMIN_PERMS) {
+		*accmode &= ~VADMIN_PERMS;
+		*accmode |= VADMIN;
+	}
+
+	/*
+	 * There is no way to deny VREAD_ATTRIBUTES, VREAD_ACL
+	 * or VSYNCHRONIZE using file mode or POSIX.1e ACL.
+	 */
+	*accmode &= ~(VSTAT_PERMS | VSYNCHRONIZE);
+
+	return (0);
+}