Update fd_freefile when filtering/closing kqueue descriptors in fdcopy().

Prior to r1.153 of kern_descrip.c, the kqueue descriptors were removed
using fdremove(), which reset fd_freefile as appropriate. The new code
simply avoids adding the descriptor to the new table, however this means
that fd_freefile can be left with an incorrect value, resulting in a file
descriptor allocation "hole". Restore the previous behavour by lowering
fd_freefile as appropriate when dropping descriptors.

Issue found via golang regress tests.

ok deraadt@ mpi@ visa@

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 831d801..4224a87 100644 (file)
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: kern_descrip.c,v 1.177 2018/07/10 08:58:50 mpi Exp $  */
+/*     $OpenBSD: kern_descrip.c,v 1.178 2018/08/10 15:53:49 jsing Exp $        */
 /*     $NetBSD: kern_descrip.c,v 1.42 1996/03/30 22:24:38 christos Exp $       */
 
 /*
@@ -1143,8 +1143,11 @@ fdcopy(struct process *pr)
                         * their internal consistency, so close them here.
                         */
                        if (fp->f_count >= FDUP_MAX_COUNT ||
-                           fp->f_type == DTYPE_KQUEUE)
+                           fp->f_type == DTYPE_KQUEUE) {
+                               if (i < newfdp->fd_freefile)
+                                       newfdp->fd_freefile = i;
                                continue;
+                       }
 
                        FREF(fp);
                        newfdp->fd_ofiles[i] = fp;