git: 77dd10b2408e - stable/15 - ipfilter: Validate length before checksum

The branch stable/15 has been updated by cy:

URL: https://cgit.FreeBSD.org/src/commit/?id=77dd10b2408eced1ac9eb63e27658491bf3ef701

commit 77dd10b2408eced1ac9eb63e27658491bf3ef701
Author:     Cy Schubert <cy@FreeBSD.org>
AuthorDate: 2026-05-11 15:44:52 +0000
Commit:     Cy Schubert <cy@FreeBSD.org>
CommitDate: 2026-05-27 13:41:25 +0000

    ipfilter: Validate length before checksum
    
    Validate the length of the packet listed in the mbuf is the same as
    the calculated packet length. If not reject the packet and bump the
    bad packet stat.
    
    PR:             295198
    Differential Revision:  https://reviews.freebsd.org/D57095
    
    (cherry picked from commit 8dfb0805fc31cd78940429ab0560dae7e8ab6536)
---
 sys/netpfil/ipfilter/netinet/fil.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/sys/netpfil/ipfilter/netinet/fil.c b/sys/netpfil/ipfilter/netinet/fil.c
index 09640623fdf2..8acf37c4c81f 100644
--- a/sys/netpfil/ipfilter/netinet/fil.c
+++ b/sys/netpfil/ipfilter/netinet/fil.c
@@ -1991,7 +1991,7 @@ ipf_checkcipso(fr_info_t *fin, u_char *s, int ol)
 
 /* ------------------------------------------------------------------------ */
 /* Function:    ipf_makefrip                                                */
-/* Returns:     int     - 0 == packet ok, -1 == packet freed                */
+/* Returns:     int     - 0 == packet ok, -1 == packet freed or bad length  */
 /* Parameters:  hlen(I) - length of IP packet header                        */
 /*              ip(I)   - pointer to the IP header                          */
 /*              fin(IO) - pointer to packet information                     */
@@ -2019,14 +2019,23 @@ ipf_makefrip(int hlen, ip_t *ip, fr_info_t *fin)
 	if (v == 4) {
 		fin->fin_plen = ntohs(ip->ip_len);
 		fin->fin_dlen = fin->fin_plen - hlen;
-		ipf_pr_ipv4hdr(fin);
+		if (fin->fin_m != NULL && fin->fin_m->m_flags & M_PKTHDR && fin->fin_m->m_pkthdr.len < fin->fin_plen) {
+			LBUMPD(ipf_stats[fin->fin_out], fr_bad);
+			return (-1);
+		} else {
+			ipf_pr_ipv4hdr(fin);
+		}
 #ifdef	USE_INET6
 	} else if (v == 6) {
 		fin->fin_plen = ntohs(((ip6_t *)ip)->ip6_plen);
 		fin->fin_dlen = fin->fin_plen;
 		fin->fin_plen += hlen;
-
-		ipf_pr_ipv6hdr(fin);
+		if (fin->fin_m != NULL && fin->fin_m->m_flags & M_PKTHDR && fin->fin_m->m_pkthdr.len < fin->fin_plen) {
+			LBUMPD(ipf_stats[fin->fin_out], fr_v6_bad);
+			return (-1);
+		} else {
+			ipf_pr_ipv6hdr(fin);
+		}
 #endif
 	}
 	if (fin->fin_ip == NULL) {