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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:
Andrey V. Elsukov 2018-11-27 09:04:06 +00:00
parent 71cf0a4e29
commit a716ad4a35
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=341008
2 changed files with 7 additions and 1 deletions
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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;