From: Martin KaFai Lau <martin.lau@kernel.org> mainline inclusion from mainline-v6.19-rc1 commit d946f3c98328171fa50ddb908593cf833587f725 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/12719 CVE: CVE-2025-68363 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The bpf_skb_check_mtu helper needs to use skb->transport_header when the BPF_MTU_CHK_SEGS flag is used: bpf_skb_check_mtu(skb, ifindex, &mtu_len, 0, BPF_MTU_CHK_SEGS) The transport_header is not always set. There is a WARN_ON_ONCE report when CONFIG_DEBUG_NET is enabled + skb->gso_size is set + bpf_prog_test_run is used: WARNING: CPU: 1 PID: 2216 at ./include/linux/skbuff.h:3071 skb_gso_validate_network_len bpf_skb_check_mtu bpf_prog_3920e25740a41171_tc_chk_segs_flag # A test in the next patch bpf_test_run bpf_prog_test_run_skb For a normal ingress skb (not test_run), skb_reset_transport_header is performed but there is plan to avoid setting it as described in commit 2170a1f09148 ("net: no longer reset transport_header in __netif_receive_skb_core()"). This patch fixes the bpf helper by checking skb_transport_header_was_set(). The check is done just before skb->transport_header is used, to avoid breaking the existing bpf prog. The WARN_ON_ONCE is limited to bpf_prog_test_run, so targeting bpf-next. Fixes: 34b2021cc616 ("bpf: Add BPF-helper for MTU checking") Cc: Jesper Dangaard Brouer <hawk@kernel.org> Reported-by: Kaiyan Mei <M202472210@hust.edu.cn> Reported-by: Yinhao Hu <dddddd@hust.edu.cn> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Link: https://lore.kernel.org/r/20251112232331.1566074-1-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- net/core/filter.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index c9d4910f3f55..c8bb4537e0fc 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6360,9 +6360,12 @@ BPF_CALL_5(bpf_skb_check_mtu, struct sk_buff *, skb, */ if (skb_is_gso(skb)) { ret = BPF_MTU_CHK_RET_SUCCESS; - if (flags & BPF_MTU_CHK_SEGS && - !skb_gso_validate_network_len(skb, mtu)) - ret = BPF_MTU_CHK_RET_SEGS_TOOBIG; + if (flags & BPF_MTU_CHK_SEGS) { + if (!skb_transport_header_was_set(skb)) + return -EINVAL; + if (!skb_gso_validate_network_len(skb, mtu)) + ret = BPF_MTU_CHK_RET_SEGS_TOOBIG; + } } out: *mtu_len = mtu; -- 2.25.1