[src/trunk]: src/sys/kern ksymsmmap: Add missing uao_reference(9) call for ks...

[rin <rin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/dce5fc381ee2
branches:  trunk
changeset: 986998:dce5fc381ee2
user:      rin <rin%NetBSD.org@localhost>
date:      Wed Sep 22 05:42:19 2021 +0000

description:
ksymsmmap: Add missing uao_reference(9) call for ks->ks_uobj.

Fix failure for savecore(8) and subsequent kernel panic, introduced to
kern_ksyms.c rev 1.03, at least for sh3 and alpha.

For sh3 and alpha, savecore(8) supports coff and ecoff, respectively, via
libkvm via nlist(3). nlist(3) routines for coff and ecoff use mmap(2) and
munmap(2) for /dev/ksyms.

This munmap(2) decrements reference count for ks->ks_uobj. Unless it is
incremented in ksymsmmap(), ks->ks_uobj will be freed unexpectedly.

diffstat:

 sys/kern/kern_ksyms.c |  5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diffs (26 lines):

diff -r acc7bc3d3cad -r dce5fc381ee2 sys/kern/kern_ksyms.c
--- a/sys/kern/kern_ksyms.c     Tue Sep 21 23:06:18 2021 +0000
+++ b/sys/kern/kern_ksyms.c     Wed Sep 22 05:42:19 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_ksyms.c,v 1.104 2021/09/11 10:09:55 riastradh Exp $       */
+/*     $NetBSD: kern_ksyms.c,v 1.105 2021/09/22 05:42:19 rin Exp $     */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -73,7 +73,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.104 2021/09/11 10:09:55 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.105 2021/09/22 05:42:19 rin Exp $");
 
 #if defined(_KERNEL) && defined(_KERNEL_OPT)
 #include "opt_copy_symtab.h"
@@ -1406,6 +1406,7 @@
                return EINVAL;  /* XXX ??? */
 
        /* Success!  */
+       uao_reference(ks->ks_uobj);
        *advicep = UVM_ADV_SEQUENTIAL;
        *uobjp = ks->ks_uobj;
        *maxprotp = prot & VM_PROT_READ;