From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f53.google.com (mail-pj1-f53.google.com [209.85.216.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 402A9372066 for ; Fri, 15 May 2026 05:55:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778824543; cv=none; b=HE4LOw9iswWU6gcsTGqv1Gz79RnVul6uPfHaf4uXa+bPVlCeU3lbMDTtz9+KQvldsh6tuMIDKNXHWL/rRdKWj86uGz6aK4SbtyE2wt/grjLDhOA1qdyGdN4SAd3za48akQPwJrO8Rxorwcc9sLIpMZ9dc+jC3984fOUM2CbwDkI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778824543; c=relaxed/simple; bh=kiGBY43ZgTHH+8dj2AvY07Oa87W2raHsSDpHldiKLfw=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=Ybgz+w2OawHkbw76c+4ftdxLlubnjZ/Yg3NXk5/Cd+Al7IqEoaBzum7UwZKLXmUtvfsEGj4P7b6jiLyEXSSfR/t+d2gi1cd/5A04sjqTN84wqrs5PXfae2stOO8XOl4WNXhHFjznD3Et5thztopjLSBVwfaaMSZsWUVcoOtmIyk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=SKrHLgRd; arc=none smtp.client-ip=209.85.216.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SKrHLgRd" Received: by mail-pj1-f53.google.com with SMTP id 98e67ed59e1d1-366070f71adso8074668a91.2 for ; Thu, 14 May 2026 22:55:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1778824541; x=1779429341; darn=vger.kernel.org; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :from:to:cc:subject:date:message-id:reply-to; bh=R7u2xRDtI3zLL+092m8rkgcne2y/yfPHTwkHpvlenKo=; b=SKrHLgRdhfLab8XJjKPnyL2I6XFda40ZXXm7A/qmLs34unSLqB6j3M2HzbpJxmUF5R xf40MlkZJOPZJQ20RBGfRidi8KhOpyx+Nuo8mZ9dujCXV7dTKgI6X3fzrBS7pgICve/x ckk+SneDbb7jxK3GqbKPcAqNrChhL/8wlbBdn0KKjk+zjfeq9OtqexELmQHzUYQbjMjd 9sWKu8EKpo3ruWnacHAeqTz3YJXbG6zd6ksCQNF10tX9W85bTOQoz/taFzMYUmeOkqxa evG24h7mKNGnEMHzpoJSQQNs4iLB0P6uASQWB2q+iuPTBwbE0yRFUeJFiup9QVGxBcwI cv8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778824541; x=1779429341; h=content-disposition:mime-version:message-id:subject:cc:to:from:date :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=R7u2xRDtI3zLL+092m8rkgcne2y/yfPHTwkHpvlenKo=; b=IkK9c18Ip0mt1i24JRFT8OvLHPk0SIVHF46hDUuliIwcohdvZ10Uzcr67dC02kvpvd 9kVR2v56uyh/yqQhLcrASm5QjXMdR2TvmlqrF8KkevRYthF75MkV3avWZxw1HM76AZwN RGV2n6S6yrECTDqHz4nzkoqqkrYhx0u3f1TuV4/0wLzJ3zS93Rj+l6PNsL2ynsvTvowb DrcKbP5B0OkilYcmpYRG8/3hAgbFy1DmRaOyXtQP3TnWJ48sA4db/VQuwoqTqG7fZWjn 003MLJynm1iEfMCitaE98vW6rFWxM4rQhG1kztbmp55nK2K5AuI0sYagCfw6N9EAlqNH osOw== X-Forwarded-Encrypted: i=1; AFNElJ8FYQgUi6D7I6koSo+JntnrOBEc8BDEQVHZ4FxEMx6urU7ORFLsNxxi4ykO8n5y5oICtD/Lhak=@vger.kernel.org X-Gm-Message-State: AOJu0Yz3c7wMkLTTcu7JLFTGg39SAFBPFmQQ7vqP6GWmE4ygmYsSSYrZ 4ElpBhWQ9b/1lCsmZ9J2Th9U3rDipKhVMW8ZqcQ2MDcYT5NkV6dbRbk6WLYHOd+5 X-Gm-Gg: Acq92OGsIO97X0sjIuqI6rNiEhmTSnvuTGJTwQK3d+7fB35DetSiJk6FShiiMm7rA4L qsfxPfsWjO7ECMh1uGbk7gAOD8Xwr3aMpeUhtmBg9UtTfUnpQdNW1q/Hw0iyT4DmkC73GcwgjMG t2wSv8Jvz/wudS+34ml7rvIb96MaQSSc8j7sQ4toHW5lrj93ydeUrLarl6Ts0TGU+rtMpCcr2m2 KtC8S7kjq0wTHhgScTe8n5irbB8/my0Qze6cmiPK8zO48VX0mq+CW+5W1Obry/7faHbYw6t7q/z 8c4+AvkkBj0GZxbum3Tt+LK1QJbKtuOQvfD8B6l3kuua8M1eARhBeXX97uSilmIcF1K1G+GCdr4 XTkhjo9avrDP4c/RuOv+9OTMW/8oqt7/HXv0Zdm4owylOlqokibs0CiTjl8ePfOeB4PVVfuNOe3 Q1WRDchlF7isszxi1QbdxmOy5OZTs2x9fBoY/Y4wU9WVKxRBxhE4VlJw== X-Received: by 2002:a17:90b:4d0e:b0:367:cb53:7435 with SMTP id 98e67ed59e1d1-36951caf2b3mr2499377a91.24.1778824541434; Thu, 14 May 2026 22:55:41 -0700 (PDT) Received: from v4bel ([58.123.110.97]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3695155b2c4sm1503887a91.3.2026.05.14.22.55.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 May 2026 22:55:40 -0700 (PDT) Date: Fri, 15 May 2026 14:55:35 +0900 From: Hyunwoo Kim To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, kerneljasonxing@gmail.com, kuniyu@google.com, mhal@rbox.co, jiayuan.chen@linux.dev, steffen.klassert@secunet.com, ben@decadent.org.uk, herbert@gondor.apana.org.au, dsahern@kernel.org, sultan@kerneltoast.com, sd@queasysnail.net Cc: netdev@vger.kernel.org, stable@vger.kernel.org, imv4bel@gmail.com Subject: [PATCH net v4] net: skbuff: propagate shared-frag marker through frag-transfer helpers Message-ID: Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Two frag-transfer helpers (__pskb_copy_fclone() and skb_shift()) fail to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()->flags when moving frags from source to destination. __pskb_copy_fclone() defers the rest of the shinfo metadata to skb_copy_header() after copying frag descriptors, but that helper only carries over gso_{size,segs, type} and never touches skb_shinfo()->flags; skb_shift() moves frag descriptors directly and leaves flags untouched. As a result, the destination skb keeps a reference to the same externally-owned or page-cache-backed pages while reporting skb_has_shared_frag() as false. The mismatch is harmful in any in-place writer that uses skb_has_shared_frag() to decide whether shared pages must be detoured through skb_cow_data(). ESP input is one such writer (esp4.c, esp6.c), and a single nft 'dup to ' rule -- or any other nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d skb in esp_input() with the marker stripped, letting an unprivileged user write into the page cache of a root-owned read-only file via authencesn-ESN stray writes. Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors were actually moved from the source. skb_copy() and skb_copy_expand() share skb_copy_header() too but linearize all paged data into freshly allocated head storage and emerge with nr_frags == 0, so skb_has_shared_frag() returns false on its own; they need no change. The same omission exists in skb_gro_receive() and skb_gro_receive_list(). The former moves the incoming skb's frag descriptors into the accumulator's last sub-skb via two paths (a direct frag-move loop and the head_frag + memcpy path); the latter chains the incoming skb whole onto p's frag_list. Downstream skb_segment() reads only skb_shinfo(p)->flags, and skb_segment_list() reuses each sub-skb's shinfo as the nskb -- both p and lp must carry the marker. The same omission also exists in tcp_clone_payload(), which builds an MTU probe skb by moving frag descriptors from skbs on sk_write_queue into a freshly allocated nskb. The helper falls into the same family and warrants the same fix for consistency; no TCP TX-side in-place writer is currently known to reach a user page through this gap, but a future consumer depending on the marker would regress silently. Fixes: cef401de7be8 ("net: fix possible wrong checksum generation") Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags") Suggested-by: Sabrina Dubroca Suggested-by: Sultan Alsawaf Suggested-by: Ben Hutchings Cc: stable@vger.kernel.org Signed-off-by: Hyunwoo Kim --- Changes in v4: - Include the tcp_clone_payload() propagation suggested by Sabrina. - Drop the skb_try_coalesce() change; addressed by commit f84eca581739. - v3: https://lore.kernel.org/all/agW4vC0r8QOUKtRT@v4bel/ Changes in v3: - Include the skb_gro_receive() audit patch suggested by Sultan - v2: https://lore.kernel.org/all/agToIEDI4TaTNLRb@v4bel/ Changes in v2: - Also propagate SHARED_FRAG in skb_try_coalesce() and skb_shift() - v1: https://lore.kernel.org/all/agRfuVOeMI5pbHhY@v4bel/ --- net/core/gro.c | 4 ++++ net/core/skbuff.c | 3 +++ net/ipv4/tcp_output.c | 1 + 3 files changed, 8 insertions(+) diff --git a/net/core/gro.c b/net/core/gro.c index 31d21de5b15a..9f8960789b2c 100644 --- a/net/core/gro.c +++ b/net/core/gro.c @@ -213,10 +213,12 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb) p->data_len += len; p->truesize += delta_truesize; p->len += len; + skb_shinfo(p)->flags |= skbinfo->flags & SKBFL_SHARED_FRAG; if (lp != p) { lp->data_len += len; lp->truesize += delta_truesize; lp->len += len; + skb_shinfo(lp)->flags |= skbinfo->flags & SKBFL_SHARED_FRAG; } NAPI_GRO_CB(skb)->same_flow = 1; return 0; @@ -244,6 +246,8 @@ int skb_gro_receive_list(struct sk_buff *p, struct sk_buff *skb) p->truesize += skb->truesize; p->len += skb->len; + skb_shinfo(p)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG; + NAPI_GRO_CB(skb)->same_flow = 1; return 0; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 9c4e8d331d6d..7cd388504297 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2248,6 +2248,7 @@ struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom, skb_frag_ref(skb, i); } skb_shinfo(n)->nr_frags = i; + skb_shinfo(n)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG; } if (skb_has_frag_list(skb)) { @@ -4349,6 +4350,8 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen) tgt->ip_summed = CHECKSUM_PARTIAL; skb->ip_summed = CHECKSUM_PARTIAL; + skb_shinfo(tgt)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG; + skb_len_add(skb, -shiftlen); skb_len_add(tgt, shiftlen); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index f9d8755705f7..6e4bb411dc04 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2626,6 +2626,7 @@ static int tcp_clone_payload(struct sock *sk, struct sk_buff *to, todo = min_t(int, skb_frag_size(fragfrom), probe_size - len); len += todo; + skb_shinfo(to)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG; if (lastfrag && skb_frag_page(fragfrom) == skb_frag_page(lastfrag) && skb_frag_off(fragfrom) == skb_frag_off(lastfrag) + -- 2.43.0