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Fix possible panic during ifnet detach in rtsock.

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The panic can happen, when some application does dump of routing table
using sysctl interface. To prevent this, set IFF_DYING flag in
if_detach_internal() function, when ifnet under lock is removed from
the chain. In sysctl_rtsock() take IFNET_RLOCK_NOSLEEP() to prevent
ifnet detach during routes enumeration. In case, if some interface was
detached in the time before we take the lock, add the check, that ifnet
is not DYING. This prevents access to memory that could be freed after
ifnet is unlinked.

PR:		227720, 230498, 233306
Reviewed by:	bz, eugen
MFC after:	1 week
Sponsored by:	Yandex LLC
Differential Revision:	https://reviews.freebsd.org/D18338
This commit is contained in:
ae 2018-11-27 09:04:06 +00:00
parent a9b758a791
commit 4e66e79020
2 changed files with 7 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
sys/net/if.c
View File

@ -1068,6 +1068,8 @@ if_detach_internal(struct ifnet *ifp, int vmove, struct if_clone **ifcp)
CK_STAILQ_FOREACH(iter, &V_ifnet, if_link)
if (iter == ifp) {
CK_STAILQ_REMOVE(&V_ifnet, ifp, ifnet, if_link);
if (!vmove)
ifp->if_flags |= IFF_DYING;
found = 1;
break;
}

6
sys/net/rtsock.c
View File

@ -1559,6 +1559,8 @@ sysctl_dumpentry(struct radix_node *rn, void *vw)
struct rt_addrinfo info;
struct sockaddr_storage ss;
IFNET_RLOCK_NOSLEEP_ASSERT();
if (w->w_op == NET_RT_FLAGS && !(rt->rt_flags & w->w_arg))
return 0;
if ((rt->rt_flags & RTF_HOST) == 0
@ -1571,7 +1573,7 @@ sysctl_dumpentry(struct radix_node *rn, void *vw)
info.rti_info[RTAX_NETMASK] = rtsock_fix_netmask(rt_key(rt),
rt_mask(rt), &ss);
info.rti_info[RTAX_GENMASK] = 0;
if (rt->rt_ifp) {
if (rt->rt_ifp && !(rt->rt_ifp->if_flags & IFF_DYING)) {
info.rti_info[RTAX_IFP] = rt->rt_ifp->if_addr->ifa_addr;
info.rti_info[RTAX_IFA] = rt->rt_ifa->ifa_addr;
if (rt->rt_ifp->if_flags & IFF_POINTOPOINT)
@ -1934,8 +1936,10 @@ sysctl_rtsock(SYSCTL_HANDLER_ARGS)
rnh = rt_tables_get_rnh(fib, i);
if (rnh != NULL) {
RIB_RLOCK(rnh);
IFNET_RLOCK_NOSLEEP();
error = rnh->rnh_walktree(&rnh->head,
sysctl_dumpentry, &w);
IFNET_RUNLOCK_NOSLEEP();
RIB_RUNLOCK(rnh);
} else if (af != 0)
error = EAFNOSUPPORT;