Messages in this thread |  | | Date | Tue, 5 May 2026 03:01:15 +0900 | | From | Hyunwoo Kim <> | | Subject | Re: [PATCH net v2] xfrm: esp: avoid in-place decrypt on shared skb frags |
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On Mon, May 04, 2026 at 11:27:12PM +0800, HexRabbit wrote: > From: Kuan-Ting Chen <h3xrabbit@gmail.com> > > MSG_SPLICE_PAGES can attach pages from a pipe directly to an skb. TCP > marks such skbs with SKBFL_SHARED_FRAG after skb_splice_from_iter(), > so later paths that may modify packet data can first make a private > copy. The IPv4/IPv6 datagram append paths did not set this flag when > splicing pages into UDP skbs. > > That leaves an ESP-in-UDP packet made from shared pipe pages looking > like an ordinary uncloned nonlinear skb. ESP input then takes the no-COW > fast path for uncloned skbs without a frag_list and decrypts in place > over data that is not owned privately by the skb. > > Mark IPv4/IPv6 datagram splice frags with SKBFL_SHARED_FRAG, matching > TCP. Also make ESP input fall back to skb_cow_data() when the flag is > present, so ESP does not decrypt externally backed frags in place. > Private nonlinear skb frags still use the existing fast path. > > This intentionally does not change ESP output. In esp_output_head(), > the path that appends the ESP trailer to existing skb tailroom without > calling skb_cow_data() is not reachable for nonlinear skbs: > skb_tailroom() returns zero when skb->data_len is nonzero, while ESP > tailen is positive. Thus ESP output will either use the separate > destination-frag path or fall back to skb_cow_data(). > > Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible") > Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible") > Fixes: 7da0dde68486 ("ip, udp: Support MSG_SPLICE_PAGES") > Fixes: 6d8192bd69bb ("ip6, udp6: Support MSG_SPLICE_PAGES") > Reported-by: Hyunwoo Kim <imv4bel@gmail.com> > Reported-by: Kuan-Ting Chen <h3xrabbit@gmail.com>
I dynamically tested this patch and confirm it resolves the issue. Clean work.
One correction request before merge -- please drop the second Reported-by tag (your own) from the trailer.
The report and patch for this issue were already posted on the public netdev ML 6 days ago, i.e., the bug was already publicly reported:
https://lore.kernel.org/all/afLDKSvAvMwGh7Fy@v4bel/
Credit for patch authorship is adequately covered by Signed-off-by alone. Setting aside that your work proceeded independently rather than as a review of my earlier submission, the trailer should conform to convention to avoid future misunderstanding.
No objections to the patch itself.
Best regards, Hyunwoo Kim
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