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| author | Martin KaFai Lau <martin.lau@kernel.org> | 2025-11-13 02:23:30 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2025-11-15 05:49:18 +0300 |
| commit | d946f3c98328171fa50ddb908593cf833587f725 (patch) | |
| tree | ea068f29f238ac1278942ca44bb5bf94c17b3bcd | |
| parent | 4f7bc83b983743b439e36b4d30883a87b371cba3 (diff) | |
| download | linux-d946f3c98328171fa50ddb908593cf833587f725.tar.xz | |
bpf: Check skb->transport_header is set in bpf_skb_check_mtu
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>
| -rw-r--r-- | net/core/filter.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 1efec0d70d78..df6ce85e48dc 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6429,9 +6429,12 @@ 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; |