[src/trunk]: src/sbin/savecore Avoid overflows when reading strings.

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

details:   https://anonhg.NetBSD.org/src/rev/deb1b9db55b7
branches:  trunk
changeset: 746534:deb1b9db55b7
user:      maxv <maxv%NetBSD.org@localhost>
date:      Fri Apr 03 19:09:43 2020 +0000

description:
Avoid overflows when reading strings.

diffstat:

 sbin/savecore/savecore.c |  24 ++++++++++++++++++------
 1 files changed, 18 insertions(+), 6 deletions(-)

diffs (61 lines):

diff -r 52da50b6e6a7 -r deb1b9db55b7 sbin/savecore/savecore.c
--- a/sbin/savecore/savecore.c  Fri Apr 03 18:44:50 2020 +0000
+++ b/sbin/savecore/savecore.c  Fri Apr 03 19:09:43 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: savecore.c,v 1.89 2019/11/06 07:29:08 mrg Exp $        */
+/*     $NetBSD: savecore.c,v 1.90 2020/04/03 19:09:43 maxv Exp $       */
 
 /*-
  * Copyright (c) 1986, 1992, 1993
@@ -39,7 +39,7 @@
 #if 0
 static char sccsid[] = "@(#)savecore.c 8.5 (Berkeley) 4/28/95";
 #else
-__RCSID("$NetBSD: savecore.c,v 1.89 2019/11/06 07:29:08 mrg Exp $");
+__RCSID("$NetBSD: savecore.c,v 1.90 2020/04/03 19:09:43 maxv Exp $");
 #endif
 #endif /* not lint */
 
@@ -275,6 +275,20 @@
 }
 
 static void
+read_string(kvm_t *kd, u_long kva, char *buf, size_t size)
+{
+       size_t i;
+
+       for (i = 0; i < size - 1; i++) {
+               (void)kvm_read(kd, kva + i, buf + i, 1);
+               if (buf[i] == '\0')
+                       return;
+       }
+
+       buf[size - 1] = '\0';
+}
+
+static void
 kmem_setup(int verbose)
 {
        long l_dumplo;
@@ -331,9 +345,8 @@
                    (long long)dumplo, (long)(dumplo / DEV_BSIZE), (long)DEV_BSIZE);
        KREAD_LOGWARN(kd_kern, current_nl[X_DUMPMAG].n_value, dumpmag, exit(1));
 
-       (void)kvm_read(kd_kern, current_nl[X_VERSION].n_value, vers,
+       read_string(kd_kern, current_nl[X_VERSION].n_value, vers,
            sizeof(vers));
-       vers[sizeof(vers) - 1] = '\0';
 
        if (current_nl[X_DUMPCDEV].n_value != 0) {
                KREAD_LOGWARN(kd_kern, current_nl[X_DUMPCDEV].n_value, dumpcdev,
@@ -395,9 +408,8 @@
        long panicloc, panicstart, panicend;
        char core_vers[1024];
 
-       (void)kvm_read(kd_dump, dump_nl[X_VERSION].n_value, core_vers,
+       read_string(kd_dump, dump_nl[X_VERSION].n_value, core_vers,
            sizeof(core_vers));
-       core_vers[sizeof(core_vers) - 1] = '\0';
 
        if (strcmp(vers, core_vers) != 0)
                syslog(LOG_WARNING,