From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C95A61E49F for ; Fri, 22 May 2026 07:39:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779435577; cv=none; b=qFkWA8ziOKnVnfhcTxZ0g6yRcC+DuuFCIeKOYSVa1PkP0kTBaaEIdfh/25p0ClflcB7FgoOkoNCOxI+ReP1T4AE1I5qEncHgRzZ2+7tBlLe4lAe7PSezel9eADAYpT/dozgIO29XhZD8diolYMstmiFsbARqDWWGMLHRUFSB+BY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779435577; c=relaxed/simple; bh=gnxgukPHXG8ENmGGSH2upB5OIC6JiIX5z4R8wlTKh8A=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=LlEZti0E+yYCMHZIFfN3z1unpOOEaWop4hZ/nwrPKVB2u/MKtjIKLWpR2UTub8aEQOukEwRij5694E+/d543VN1/RPVkhrF6dsQpv6wYJf+K/7Wvmc/ssxmKpHjWRwRnwe4dXc7MXtNi15oJlXNxgMKxp5jjjDZnXBgSm4Wrywo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qeX1+hBY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="qeX1+hBY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E38D31F000E9; Fri, 22 May 2026 07:39:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779435575; bh=tiruPKDzl2PP5A8BX1Eln59aeZqFA4lBkTAGHMLjKSc=; h=Subject:To:Cc:From:Date; b=qeX1+hBYlrUCow+rxSn91OUALUMUCV963yoJ6nfA4xEDkV1dA4ssVlXGMKJ+YprKZ 8HLWdnbF6W5QfY7UvLHcTS+rAwCnrQ/ZBWILho9Znyq8cG4itgO7RpVBSw1jOizLna 7upOaRlMuM7EQ1QoGoO8McP8SCMdYfE71/oZyL8s= Subject: FAILED: patch "[PATCH] net: skbuff: propagate shared-frag marker through" failed to apply to 5.15-stable tree To: imv4bel@gmail.com,aaron1esau@gmail.com,ben@decadent.org.uk,malin89@huawei.com,pabeni@redhat.com,rajat.gupta@oss.qualcomm.com,sd@queasysnail.net,sultan@kerneltoast.com,tanjingguo@huawei.com Cc: From: Date: Fri, 22 May 2026 09:39:30 +0200 Message-ID: <2026052230-kilogram-proving-cd58@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 48f6a5356a33dd78e7144ae1faef95ffc990aae0 # git commit -s git send-email --to '' --in-reply-to '2026052230-kilogram-proving-cd58@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 48f6a5356a33dd78e7144ae1faef95ffc990aae0 Mon Sep 17 00:00:00 2001 From: Hyunwoo Kim Date: Sat, 16 May 2026 07:28:53 +0900 Subject: [PATCH] net: skbuff: propagate shared-frag marker through frag-transfer helpers 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. The same omission exists in skb_segment(): the per-iteration flag merge takes only head_skb's flag, and the inner switch that rebinds frag_skb to list_skb on head_skb-frags exhaustion does not fold the new frag_skb's flag into nskb. Fold frag_skb's flag at both sites so segments drawing frags from frag_list members carry the marker. 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 Suggested-by: Lin Ma Suggested-by: Jingguo Tan Suggested-by: Aaron Esau Cc: stable@vger.kernel.org Signed-off-by: Hyunwoo Kim Tested-by: Rajat Gupta Link: https://patch.msgid.link/ageeJfJHwgzmKXbh@v4bel Signed-off-by: Paolo Abeni 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..44ac121cfccb 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); @@ -4959,7 +4962,8 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, skb_copy_from_linear_data_offset(head_skb, offset, skb_put(nskb, hsize), hsize); - skb_shinfo(nskb)->flags |= skb_shinfo(head_skb)->flags & + skb_shinfo(nskb)->flags |= (skb_shinfo(head_skb)->flags | + skb_shinfo(frag_skb)->flags) & SKBFL_SHARED_FRAG; if (skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC)) @@ -4976,6 +4980,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, nfrags = skb_shinfo(list_skb)->nr_frags; frag = skb_shinfo(list_skb)->frags; frag_skb = list_skb; + + skb_shinfo(nskb)->flags |= skb_shinfo(frag_skb)->flags & SKBFL_SHARED_FRAG; + if (!skb_headlen(list_skb)) { BUG_ON(!nfrags); } else { 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) +