+++ /dev/null
-From 48f6a5356a33dd78e7144ae1faef95ffc990aae0 Mon Sep 17 00:00:00 2001
-From: Hyunwoo Kim <imv4bel@gmail.com>
-Date: Sat, 16 May 2026 07:28:53 +0900
-Subject: net: skbuff: propagate shared-frag marker through frag-transfer helpers
-
-From: Hyunwoo Kim <imv4bel@gmail.com>
-
-commit 48f6a5356a33dd78e7144ae1faef95ffc990aae0 upstream.
-
-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 <local>' 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 <sd@queasysnail.net>
-Suggested-by: Sultan Alsawaf <sultan@kerneltoast.com>
-Suggested-by: Ben Hutchings <ben@decadent.org.uk>
-Suggested-by: Lin Ma <malin89@huawei.com>
-Suggested-by: Jingguo Tan <tanjingguo@huawei.com>
-Suggested-by: Aaron Esau <aaron1esau@gmail.com>
-Cc: stable@vger.kernel.org
-Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
-Tested-by: Rajat Gupta <rajat.gupta@oss.qualcomm.com>
-Link: https://patch.msgid.link/ageeJfJHwgzmKXbh@v4bel
-Signed-off-by: Paolo Abeni <pabeni@redhat.com>
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
----
- net/core/gro.c | 5 +++++
- net/core/skbuff.c | 9 ++++++++-
- net/ipv4/tcp_output.c | 1 +
- 3 files changed, 14 insertions(+), 1 deletion(-)
-
---- a/net/core/gro.c
-+++ b/net/core/gro.c
-@@ -216,11 +216,16 @@ done:
- 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;
- }
-+
-+ skb_shinfo(p)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG;
-+
- NAPI_GRO_CB(skb)->same_flow = 1;
- return 0;
- }
---- a/net/core/skbuff.c
-+++ b/net/core/skbuff.c
-@@ -2050,6 +2050,7 @@ struct sk_buff *__pskb_copy_fclone(struc
- 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)) {
-@@ -4086,6 +4087,8 @@ onlymerged:
- 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);
-
-@@ -4658,7 +4661,8 @@ normal:
- 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))
-@@ -4675,6 +4679,9 @@ normal:
- 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 {
---- a/net/ipv4/tcp_output.c
-+++ b/net/ipv4/tcp_output.c
-@@ -2366,6 +2366,7 @@ static int tcp_clone_payload(struct sock
- 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) +
projects / thirdparty / kernel / stable-queue.git / commitdiff
