From: Weiming Shi <bestswngs@gmail.com> mainline inclusion from mainline-v7.0-rc5 commit 614aefe56af8e13331e50220c936fc0689cf5675 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14029 CVE: CVE-2026-23398 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- icmp_tag_validation() unconditionally dereferences the result of rcu_dereference(inet_protos[proto]) without checking for NULL. The inet_protos[] array is sparse -- only about 15 of 256 protocol numbers have registered handlers. When ip_no_pmtu_disc is set to 3 (hardened PMTU mode) and the kernel receives an ICMP Fragmentation Needed error with a quoted inner IP header containing an unregistered protocol number, the NULL dereference causes a kernel panic in softirq context. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:icmp_unreach (net/ipv4/icmp.c:1085 net/ipv4/icmp.c:1143) Call Trace: <IRQ> icmp_rcv (net/ipv4/icmp.c:1527) ip_protocol_deliver_rcu (net/ipv4/ip_input.c:207) ip_local_deliver_finish (net/ipv4/ip_input.c:242) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:573) __netif_receive_skb_one_core (net/core/dev.c:6164) process_backlog (net/core/dev.c:6628) handle_softirqs (kernel/softirq.c:561) </IRQ> Add a NULL check before accessing icmp_strict_tag_validation. If the protocol has no registered handler, return false since it cannot perform strict tag validation. Fixes: 8ed1dc44d3e9 ("ipv4: introduce hardened ip_no_pmtu_disc mode") Reported-by: Xiang Mei <xmei5@asu.edu> Signed-off-by: Weiming Shi <bestswngs@gmail.com> Link: https://patch.msgid.link/20260318130558.1050247-4-bestswngs@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Conflicts: net/ipv4/icmp.c [context conflicts] Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> --- net/ipv4/icmp.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index aed99f8..ca4e926 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -855,10 +855,12 @@ static void icmp_socket_deliver(struct sk_buff *skb, u32 info) static bool icmp_tag_validation(int proto) { + const struct net_protocol *ipprot; bool ok; rcu_read_lock(); - ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; + ipprot = rcu_dereference(inet_protos[proto]); + ok = ipprot ? ipprot->icmp_strict_tag_validation : false; rcu_read_unlock(); return ok; } -- 2.9.5