git: fc850f4f7d44 - stable/13 - netinet6: perform out-of-bounds check for loX multicast statistics

The branch stable/13 has been updated by melifaro:

URL: https://cgit.FreeBSD.org/src/commit/?id=fc850f4f7d44201210750329eeb5ca35dd04b58c

commit fc850f4f7d44201210750329eeb5ca35dd04b58c
Author:     Alexander V. Chernikov <melifaro@FreeBSD.org>
AuthorDate: 2022-07-04 20:03:06 +0000
Commit:     Alexander V. Chernikov <melifaro@FreeBSD.org>
CommitDate: 2023-01-13 21:24:10 +0000

    netinet6: perform out-of-bounds check for loX multicast statistics
    
    Currently, some per-mbuf multicast statistics is stored in
     the per-interface ip6stat.ip6s_m2m[] array of size 32 (IP6S_M2MMAX).
    Check that loopback ifindex falls within 0.. IP6S_M2MMAX-1 range to
     avoid silent data corruption. The latter cat happen with large
     number of VNETs.
    
    Reviewed by:    glebius
    Differential Revision: https://reviews.freebsd.org/D35715
    MFC after:      2 weeks
    
    (cherry picked from commit 0ed72537857bfb6ac6d19b0852a52288db79b8b0)
---
 sys/netinet6/ip6_input.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/sys/netinet6/ip6_input.c b/sys/netinet6/ip6_input.c
index 30ad9a53006a..2423b61e0b36 100644
--- a/sys/netinet6/ip6_input.c
+++ b/sys/netinet6/ip6_input.c
@@ -579,12 +579,11 @@ ip6_input(struct mbuf *m)
 			IP6STAT_INC(ip6s_mext1);
 	} else {
 		if (m->m_next) {
-			if (m->m_flags & M_LOOP) {
-				IP6STAT_INC(ip6s_m2m[V_loif->if_index]);
-			} else if (rcvif->if_index < IP6S_M2MMAX)
-				IP6STAT_INC(ip6s_m2m[rcvif->if_index]);
-			else
-				IP6STAT_INC(ip6s_m2m[0]);
+			struct ifnet *ifp = (m->m_flags & M_LOOP) ? V_loif : rcvif;
+			int ifindex = ifp->if_index;
+			if (ifindex >= IP6S_M2MMAX)
+				ifindex = 0;
+			IP6STAT_INC(ip6s_m2m[ifindex]);
 		} else
 			IP6STAT_INC(ip6s_m1);
 	}