git: ed4692b8226e - releng/15.0 - in6_mcast: Fix a race in in6p_set_source_filter()
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Date: Tue, 09 Jun 2026 19:19:47 UTC
The branch releng/15.0 has been updated by markj:
URL: https://cgit.FreeBSD.org/src/commit/?id=ed4692b8226e81e03d1cf43ed4fa8ee311c9b851
commit ed4692b8226e81e03d1cf43ed4fa8ee311c9b851
Author: Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2026-05-29 20:12:24 +0000
Commit: Mark Johnston <markj@FreeBSD.org>
CommitDate: 2026-06-08 15:39:32 +0000
in6_mcast: Fix a race in in6p_set_source_filter()
We drop the inpcb lock in order to copy in the source list, but this
leaves a window where the multicast filter structure might be freed.
This can be exploited to obtain root privileges.
In the v4 code this race is mitigated by holding the global multicast
lock across the gap.
Restructure the code to copy in filters before doing anything else, so
that there's no need to drop the inpcb lock and reason about the
correctness of doing so. Do the same in the v4 code for consistency.
Approved by: so
Security: FreeBSD-SA-26:29.ip6_multicast
Security: CVE-2026-49412
Reported by: Andrew Griffiths <andrew@calif.io>
Reported by: Maik Münch <maik@secfault-security.com>
Reviewed by: glebius
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D57347
---
sys/netinet/in_mcast.c | 39 +++++++++++++++++----------------------
sys/netinet6/in6_mcast.c | 41 +++++++++++++++++++----------------------
2 files changed, 36 insertions(+), 44 deletions(-)
diff --git a/sys/netinet/in_mcast.c b/sys/netinet/in_mcast.c
index f5b20c49ffd2..43fa96616c70 100644
--- a/sys/netinet/in_mcast.c
+++ b/sys/netinet/in_mcast.c
@@ -2523,6 +2523,7 @@ inp_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
{
struct epoch_tracker et;
struct __msfilterreq msfr;
+ struct sockaddr_storage *kss;
sockunion_t *gsa;
struct ifnet *ifp;
struct in_mfilter *imf;
@@ -2535,9 +2536,6 @@ inp_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
if (error)
return (error);
- if (msfr.msfr_nsrcs > in_mcast_maxsocksrc)
- return (ENOBUFS);
-
if ((msfr.msfr_fmode != MCAST_EXCLUDE &&
msfr.msfr_fmode != MCAST_INCLUDE))
return (EINVAL);
@@ -2550,13 +2548,24 @@ inp_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
if (!IN_MULTICAST(ntohl(gsa->sin.sin_addr.s_addr)))
return (EINVAL);
+ if (msfr.msfr_nsrcs > in_mcast_maxsocksrc)
+ return (ENOBUFS);
+ kss = mallocarray(msfr.msfr_nsrcs, sizeof(struct sockaddr_storage),
+ M_TEMP, M_WAITOK);
+ error = copyin(msfr.msfr_srcs, kss,
+ sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs);
+ if (error)
+ goto out_inp_unlocked;
+
gsa->sin.sin_port = 0; /* ignore port */
NET_EPOCH_ENTER(et);
ifp = ifnet_byindex(msfr.msfr_ifindex);
NET_EPOCH_EXIT(et); /* XXXGL: unsafe ifp */
- if (ifp == NULL)
- return (EADDRNOTAVAIL);
+ if (ifp == NULL) {
+ error = EADDRNOTAVAIL;
+ goto out_inp_unlocked;
+ }
IN_MULTI_LOCK();
@@ -2588,24 +2597,9 @@ inp_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
if (msfr.msfr_nsrcs > 0) {
struct in_msource *lims;
struct sockaddr_in *psin;
- struct sockaddr_storage *kss, *pkss;
+ struct sockaddr_storage *pkss;
int i;
- INP_WUNLOCK(inp);
-
- CTR2(KTR_IGMPV3, "%s: loading %lu source list entries",
- __func__, (unsigned long)msfr.msfr_nsrcs);
- kss = malloc(sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs,
- M_TEMP, M_WAITOK);
- error = copyin(msfr.msfr_srcs, kss,
- sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs);
- if (error) {
- free(kss, M_TEMP);
- return (error);
- }
-
- INP_WLOCK(inp);
-
/*
* Mark all source filters as UNDEFINED at t1.
* Restore new group filter mode, as imf_leave()
@@ -2640,7 +2634,6 @@ inp_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
break;
lims->imsl_st[1] = imf->imf_st[1];
}
- free(kss, M_TEMP);
}
if (error)
@@ -2677,6 +2670,8 @@ out_imf_rollback:
out_inp_locked:
INP_WUNLOCK(inp);
IN_MULTI_UNLOCK();
+out_inp_unlocked:
+ free(kss, M_TEMP);
return (error);
}
diff --git a/sys/netinet6/in6_mcast.c b/sys/netinet6/in6_mcast.c
index a6186568ecb2..4ec9f36cd9ac 100644
--- a/sys/netinet6/in6_mcast.c
+++ b/sys/netinet6/in6_mcast.c
@@ -2489,6 +2489,7 @@ in6p_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
{
struct __msfilterreq msfr;
struct epoch_tracker et;
+ struct sockaddr_storage *kss;
sockunion_t *gsa;
struct ifnet *ifp;
struct in6_mfilter *imf;
@@ -2501,9 +2502,6 @@ in6p_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
if (error)
return (error);
- if (msfr.msfr_nsrcs > in6_mcast_maxsocksrc)
- return (ENOBUFS);
-
if (msfr.msfr_fmode != MCAST_EXCLUDE &&
msfr.msfr_fmode != MCAST_INCLUDE)
return (EINVAL);
@@ -2516,19 +2514,31 @@ in6p_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
if (!IN6_IS_ADDR_MULTICAST(&gsa->sin6.sin6_addr))
return (EINVAL);
+ if (msfr.msfr_nsrcs > in6_mcast_maxsocksrc)
+ return (ENOBUFS);
+ kss = mallocarray(msfr.msfr_nsrcs, sizeof(struct sockaddr_storage),
+ M_TEMP, M_WAITOK);
+ error = copyin(msfr.msfr_srcs, kss,
+ sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs);
+ if (error)
+ goto out_in6p_unlocked;
+
gsa->sin6.sin6_port = 0; /* ignore port */
NET_EPOCH_ENTER(et);
ifp = ifnet_byindex(msfr.msfr_ifindex);
NET_EPOCH_EXIT(et);
- if (ifp == NULL)
- return (EADDRNOTAVAIL);
+ if (ifp == NULL) {
+ error = EADDRNOTAVAIL;
+ goto out_in6p_unlocked;
+ }
(void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);
/*
* Take the INP write lock.
* Check if this socket is a member of this group.
*/
+ IN6_MULTI_LOCK();
imo = in6p_findmoptions(inp);
imf = im6o_match_group(imo, ifp, &gsa->sa);
if (imf == NULL) {
@@ -2553,24 +2563,9 @@ in6p_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
if (msfr.msfr_nsrcs > 0) {
struct in6_msource *lims;
struct sockaddr_in6 *psin;
- struct sockaddr_storage *kss, *pkss;
+ struct sockaddr_storage *pkss;
int i;
- INP_WUNLOCK(inp);
-
- CTR2(KTR_MLD, "%s: loading %lu source list entries",
- __func__, (unsigned long)msfr.msfr_nsrcs);
- kss = malloc(sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs,
- M_TEMP, M_WAITOK);
- error = copyin(msfr.msfr_srcs, kss,
- sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs);
- if (error) {
- free(kss, M_TEMP);
- return (error);
- }
-
- INP_WLOCK(inp);
-
/*
* Mark all source filters as UNDEFINED at t1.
* Restore new group filter mode, as im6f_leave()
@@ -2615,7 +2610,6 @@ in6p_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
break;
lims->im6sl_st[1] = imf->im6f_st[1];
}
- free(kss, M_TEMP);
}
if (error)
@@ -2650,6 +2644,9 @@ out_im6f_rollback:
out_in6p_locked:
INP_WUNLOCK(inp);
+ IN6_MULTI_UNLOCK();
+out_in6p_unlocked:
+ free(kss, M_TEMP);
return (error);
}