[src/trunk]: src/sys/dev/pci Protect against buffer overflow.

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

details:   https://anonhg.NetBSD.org/src/rev/a9f074884247
branches:  trunk
changeset: 818818:a9f074884247
user:      pgoyette <pgoyette%NetBSD.org@localhost>
date:      Wed Nov 02 00:39:56 2016 +0000

description:
Protect against buffer overflow.

diffstat:

 sys/dev/pci/pci_subr.c |  70 +++++++++++++++++++++++++++++++++++++------------
 1 files changed, 52 insertions(+), 18 deletions(-)

diffs (125 lines):

diff -r 36c1fc9e403e -r a9f074884247 sys/dev/pci/pci_subr.c
--- a/sys/dev/pci/pci_subr.c    Wed Nov 02 00:32:59 2016 +0000
+++ b/sys/dev/pci/pci_subr.c    Wed Nov 02 00:39:56 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pci_subr.c,v 1.154 2016/10/31 09:13:20 martin Exp $    */
+/*     $NetBSD: pci_subr.c,v 1.155 2016/11/02 00:39:56 pgoyette Exp $  */
 
 /*
  * Copyright (c) 1997 Zubin D. Dittia.  All rights reserved.
@@ -40,7 +40,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pci_subr.c,v 1.154 2016/10/31 09:13:20 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pci_subr.c,v 1.155 2016/11/02 00:39:56 pgoyette Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_pci.h"
@@ -54,6 +54,7 @@
 #include <sys/module.h>
 #else
 #include <pci.h>
+#include <stdarg.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -567,6 +568,43 @@
 
 DEV_VERBOSE_DEFINE(pci);
 
+/*
+ * Append a formatted string to dest without writing more than len
+ * characters (including the trailing NUL character).  dest and len
+ * are updated for use in subsequent calls to snappendf().
+ *
+ * Returns 0 on success, a negative value if vnsprintf() fails, or
+ * a positive value if the dest buffer would have overflowed.
+ */
+
+static int __printflike(3,4)
+snappendf(char **dest, size_t *len, const char * restrict fmt, ...)
+{
+       va_list ap;
+       int count;
+
+       va_start(ap, fmt);
+       count = vsnprintf(*dest, *len, fmt, ap);
+       va_end(ap);
+
+       /* Let vsnprintf() errors bubble up to caller */
+       if (count < 0 || *len == 0)
+               return count;
+
+       /* Handle overflow */
+       if ((size_t)count >= *len) {
+               *dest += *len - 1;
+               *len = 1;
+               return 1;
+       }
+
+       /* Update dest & len to point at trailing NUL */
+       *dest += count;
+       *len -= count;
+               
+       return 0;
+}
+
 void
 pci_devinfo(pcireg_t id_reg, pcireg_t class_reg, int showclass, char *cp,
     size_t l)
@@ -577,9 +615,6 @@
        pci_revision_t revision;
        char vendor[PCI_VENDORSTR_LEN], product[PCI_PRODUCTSTR_LEN];
        const struct pci_class *classp, *subclassp, *interfacep;
-       char *ep;
-
-       ep = cp + l;
 
        pciclass = PCI_CLASS(class_reg);
        subclass = PCI_SUBCLASS(class_reg);
@@ -612,32 +647,31 @@
                interfacep++;
        }
 
-       cp += snprintf(cp, ep - cp, "%s %s", vendor, product);
+       (void)snappendf(&cp, &l, "%s %s", vendor, product);
        if (showclass) {
-               cp += snprintf(cp, ep - cp, " (");
+               (void)snappendf(&cp, &l, " (");
                if (classp->name == NULL)
-                       cp += snprintf(cp, ep - cp,
-                           "class 0x%02x, subclass 0x%02x", pciclass, subclass);
+                       (void)snappendf(&cp, &l,
+                           "class 0x%02x, subclass 0x%02x",
+                           pciclass, subclass);
                else {
                        if (subclassp == NULL || subclassp->name == NULL)
-                               cp += snprintf(cp, ep - cp,
+                               (void)snappendf(&cp, &l,
                                    "%s, subclass 0x%02x",
                                    classp->name, subclass);
                        else
-                               cp += snprintf(cp, ep - cp, "%s %s",
+                               (void)snappendf(&cp, &l, "%s %s",
                                    subclassp->name, classp->name);
                }
                if ((interfacep == NULL) || (interfacep->name == NULL)) {
                        if (interface != 0)
-                               cp += snprintf(cp, ep - cp,
-                                   ", interface 0x%02x", interface);
+                               (void)snappendf(&cp, &l, ", interface 0x%02x",
+                                   interface);
                } else if (strncmp(interfacep->name, "", 1) != 0)
-                       cp += snprintf(cp, ep - cp, ", %s",
-                           interfacep->name);
+                       (void)snappendf(&cp, &l, ", %s", interfacep->name);
                if (revision != 0)
-                       cp += snprintf(cp, ep - cp, ", revision 0x%02x",
-                           revision);
-               cp += snprintf(cp, ep - cp, ")");
+                       (void)snappendf(&cp, &l, ", revision 0x%02x", revision);
+               (void)snappendf(&cp, &l, ")");
        }
 }