Author: brooks
Date: Fri Mar 30 21:38:53 2018
New Revision: 331831
URL: https://svnweb.freebsd.org/changeset/base/331831
Log:
Document and enforce assumptions about struct (in6_)ifreq.
- The two types must be type-punnable for shared members of ifr_ifru.
This allows compatibility accessors to be shared.
- There must be no padding gap between ifr_name and ifr_ifru. This is
assumed in tcpdump's use of SIOCGIFFLAGS output which attempts to be
broadly portable. This is true for all current architectures, but very
large (256-bit) fat-pointers could violate this invariant.
Reviewed by: kib
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D14910
Modified:
head/sys/net/if.c
head/sys/netinet6/in6.c
Modified: head/sys/net/if.c
==============================================================================
--- head/sys/net/if.c Fri Mar 30 20:27:47 2018 (r331830)
+++ head/sys/net/if.c Fri Mar 30 21:38:53 2018 (r331831)
@@ -97,6 +97,13 @@
#include <security/mac/mac_framework.h>
+/*
+ * Consumers of struct ifreq such as tcpdump assume no pad between ifr_name
+ * and ifr_ifru when it is used in SIOCGIFCONF.
+ */
+_Static_assert(sizeof(((struct ifreq *)0)->ifr_name) ==
+ offsetof(struct ifreq, ifr_ifru), "gap between ifr_name and ifr_ifru");
+
#ifdef COMPAT_FREEBSD32
#include <sys/mount.h>
#include <compat/freebsd32/freebsd32.h>
Modified: head/sys/netinet6/in6.c
==============================================================================
--- head/sys/netinet6/in6.c Fri Mar 30 20:27:47 2018 (r331830)
+++ head/sys/netinet6/in6.c Fri Mar 30 21:38:53 2018 (r331831)
@@ -112,6 +112,14 @@ __FBSDID("$FreeBSD$");
#include <netinet6/in6_fib.h>
#include <netinet6/in6_pcb.h>
+/*
+ * struct in6_ifreq and struct ifreq must be type punnable for common members
+ * of ifr_ifru to allow accessors to be shared.
+ */
+_Static_assert(offsetof(struct in6_ifreq, ifr_ifru) ==
+ offsetof(struct ifreq, ifr_ifru),
+ "struct in6_ifreq and struct ifreq are not type punnable");
+
VNET_DECLARE(int, icmp6_nodeinfo_oldmcprefix);
#define V_icmp6_nodeinfo_oldmcprefix VNET(icmp6_nodeinfo_oldmcprefix)
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