+++ /dev/null
-From f84eca5817390257cef78013d0112481c503b4a3 Mon Sep 17 00:00:00 2001
-From: William Bowling <vakzz@zellic.io>
-Date: Wed, 13 May 2026 04:16:35 +0000
-Subject: net: skbuff: preserve shared-frag marker during coalescing
-
-From: William Bowling <vakzz@zellic.io>
-
-commit f84eca5817390257cef78013d0112481c503b4a3 upstream.
-
-skb_try_coalesce() can attach paged frags from @from to @to. If @from
-has SKBFL_SHARED_FRAG set, the resulting @to skb can contain the same
-externally-owned or page-cache-backed frags, but the shared-frag marker
-is currently lost.
-
-That breaks the invariant relied on by later in-place writers. In
-particular, ESP input checks skb_has_shared_frag() before deciding
-whether an uncloned nonlinear skb can skip skb_cow_data(). If TCP
-receive coalescing has moved shared frags into an unmarked skb, ESP can
-see skb_has_shared_frag() as false and decrypt in place over page-cache
-backed frags.
-
-Propagate SKBFL_SHARED_FRAG when skb_try_coalesce() transfers paged
-frags. The tailroom copy path does not need the marker because it copies
-bytes into @to's linear data rather than transferring frag descriptors.
-
-Fixes: cef401de7be8 ("net: fix possible wrong checksum generation")
-Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags")
-Signed-off-by: William Bowling <vakzz@zellic.io>
-Reviewed-by: Eric Dumazet <edumazet@google.com>
-Tested-by: Jiayuan Chen <jiayuan.chen@linux.dev>
-Link: https://patch.msgid.link/20260513041635.1289541-1-vakzz@zellic.io
-Signed-off-by: Jakub Kicinski <kuba@kernel.org>
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
----
- net/core/skbuff.c | 2 ++
- 1 file changed, 2 insertions(+)
-
---- a/net/core/skbuff.c
-+++ b/net/core/skbuff.c
-@@ -5315,6 +5315,8 @@ bool skb_try_coalesce(struct sk_buff *to
- from_shinfo->frags,
- from_shinfo->nr_frags * sizeof(skb_frag_t));
- to_shinfo->nr_frags += from_shinfo->nr_frags;
-+ if (from_shinfo->nr_frags)
-+ to_shinfo->flags |= from_shinfo->flags & SKBFL_SHARED_FRAG;
-
- if (!skb_cloned(from))
- from_shinfo->nr_frags = 0;