When nf_nat_ipv4.ko is not loaded, l3proto is NULL pointer. If the csum_recalc function of l3proto is called, it will cause NULL pointer access issue. --- v3: add space after return type for Patch 3/3 v2: modify commit message for Patch 3/3 --- Florian Westphal (2): netfilter: nat: remove csum_recalc hook netfilter: nat: fix udp checksum corruption Zhengchao Shao (1): netfilter: nat: fix kabi change include/net/netfilter/nf_nat_l3proto.h | 4 ++ net/ipv4/netfilter/nf_nat_l3proto_ipv4.c | 19 ------ net/ipv6/netfilter/nf_nat_l3proto_ipv6.c | 19 ------ net/netfilter/Makefile | 2 +- net/netfilter/nf_nat_helper.c | 12 ++-- net/netfilter/nf_nat_proto.c | 74 ++++++++++++++++++++++++ 6 files changed, 83 insertions(+), 47 deletions(-) create mode 100644 net/netfilter/nf_nat_proto.c -- 2.34.1