From: Kuan-Ting Chen Date: Mon, 4 May 2026 15:27:12 +0000 (+0800) Subject: xfrm: esp: avoid in-place decrypt on shared skb frags X-Git-Tag: v7.1-rc3~26^2~19^2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f4c50a4034e62ab75f1d5cdd191dd5f9c77fdff4;p=thirdparty%2Fkernel%2Fstable.git xfrm: esp: avoid in-place decrypt on shared skb frags 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 Reported-by: Kuan-Ting Chen Tested-by: Hyunwoo Kim Cc: stable@vger.kernel.org Signed-off-by: Kuan-Ting Chen Signed-off-by: Steffen Klassert --- diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c index 6dfc0bcdef65..6a5febbdbee4 100644 --- a/net/ipv4/esp4.c +++ b/net/ipv4/esp4.c @@ -873,7 +873,8 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb) nfrags = 1; goto skip_cow; - } else if (!skb_has_frag_list(skb)) { + } else if (!skb_has_frag_list(skb) && + !skb_has_shared_frag(skb)) { nfrags = skb_shinfo(skb)->nr_frags; nfrags++; diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index e4790cc7b5c2..5bcd73cbdb41 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -1233,6 +1233,8 @@ alloc_new_skb: if (err < 0) goto error; copy = err; + if (!(flags & MSG_NO_SHARED_FRAGS)) + skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG; wmem_alloc_delta += copy; } else if (!zc) { int i = skb_shinfo(skb)->nr_frags; diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c index 9f75313734f8..9c06c5a1419d 100644 --- a/net/ipv6/esp6.c +++ b/net/ipv6/esp6.c @@ -915,7 +915,8 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb) nfrags = 1; goto skip_cow; - } else if (!skb_has_frag_list(skb)) { + } else if (!skb_has_frag_list(skb) && + !skb_has_shared_frag(skb)) { nfrags = skb_shinfo(skb)->nr_frags; nfrags++; diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 7e92909ab5be..1f2a33fbed6e 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1794,6 +1794,8 @@ alloc_new_skb: if (err < 0) goto error; copy = err; + if (!(flags & MSG_NO_SHARED_FRAGS)) + skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG; wmem_alloc_delta += copy; } else if (!zc) { int i = skb_shinfo(skb)->nr_frags;