Bump version to 5.14.0-611.54.5
net: skbuff: propagate shared-frag marker through frag-transfer helpers Replace 611.54.4's partial fix (which was a backport of Hyunwoo Kim's v1 patch covering only __pskb_copy_fclone() and skb_try_coalesce()) with a backport of the upstream v3 patch: https://lore.kernel.org/all/agW4vC0r8QOUKtRT@v4bel/ v3 also covers skb_shift() (the new hunk added in v2) and skb_gro_receive() / skb_gro_receive_list() (the audit follow-up suggested by Sultan Alsawaf in agVpIsaSherjHTYg@sultan-box). All five sites moved frag descriptors between skbs without propagating the SKBFL_SHARED_FRAG marker, so destinations could end up referencing externally-owned or page-cache-backed pages while reporting skb_has_shared_frag() as false. Combined with ESP-over-UDP and UDP GRO, or any nf_dup_ipv4 / xt_TEE caller, this lets an unprivileged user trigger in-place ESP decryption over root-owned page-cache pages (CVE-2026-46300, "Fragnesia"). Tree-adapted: skb_gro_receive_list() is still a static helper in net/ipv4/udp_offload.c on RHEL 9 (not promoted to a global GRO helper in net/core/gro.c as in upstream v3); skb_shift() still uses the open-coded skb->len -= shiftlen block instead of skb_len_add().
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@ -1,28 +1,30 @@
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From: Andrew Lukoshko <alukoshko@almalinux.org>
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Subject: [PATCH AlmaLinux 9] net: skbuff: propagate shared-frag marker through pskb_copy()
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From: Eduard Abdullin <eabdullin@almalinux.org>
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Subject: [PATCH AlmaLinux 9] net: skbuff: propagate shared-frag marker through frag-transfer helpers
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Backport of upstream patch posted at
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https://lore.kernel.org/all/agRfuVOeMI5pbHhY@v4bel/
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(sibling to the xfrm/esp shared-frag fix already shipped as
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1100-xfrm-esp-avoid-in-place-decrypt-shared-skb-frags.patch in
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5.14.0-611.54.2).
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Backport of upstream v3 patch posted at
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https://lore.kernel.org/all/agW4vC0r8QOUKtRT@v4bel/
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(sibling to upstream commit f4c50a4034e6 "xfrm: esp: avoid in-place
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decrypt on shared skb frags").
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__pskb_copy_fclone() shallow-copies the source's frag descriptors and
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bumps each page's refcount via skb_frag_ref(), then defers the rest
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of the shinfo metadata to skb_copy_header(). That helper only carries
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over gso_{size,segs,type} and never touches skb_shinfo()->flags, so
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the destination skb keeps a reference to the same externally-owned or
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page-cache-backed pages while reporting skb_has_shared_frag() as
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false.
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Three frag-transfer helpers in net/core/skbuff.c
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(__pskb_copy_fclone(), skb_try_coalesce(), skb_shift()) and the
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GRO accumulator path in net/core/gro.c (skb_gro_receive()) and the
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UDP GRO list helper in net/ipv4/udp_offload.c
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(skb_gro_receive_list(), kept as a static helper on AlmaLinux 9)
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fail to propagate the SKBFL_SHARED_FRAG bit in skb_shinfo()->flags
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when moving frag descriptors from source to destination. As a
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result, the destination skb keeps a reference to the same
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externally-owned or page-cache-backed pages while reporting
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skb_has_shared_frag() as false.
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The mismatch is harmful in any in-place writer that uses
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skb_has_shared_frag() to decide whether shared pages must be detoured
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through skb_cow_data(). ESP input is one such writer (esp4.c,
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esp6.c), and a single nft 'dup to <local>' rule -- or any other
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nf_dup_ipv4() / xt_TEE caller -- is enough to land a pskb_copy()'d
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skb in esp_input() with the marker stripped, letting an unprivileged
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user write into the page cache of a root-owned read-only file via
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authencesn-ESN stray writes.
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esp6.c). Combined with an nft 'dup to <local>' rule, an
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nf_dup_ipv4() / xt_TEE caller, or ESP-over-UDP with UDP GRO, this
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lets an unprivileged user write into the page cache of a root-owned
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read-only file via authencesn-ESN stray writes (CVE-2026-46300,
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"Fragnesia").
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Set SKBFL_SHARED_FRAG on the destination whenever frag descriptors
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were actually moved from the source. skb_copy() and skb_copy_expand()
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@ -30,18 +32,53 @@ share skb_copy_header() too but linearize all paged data into freshly
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allocated head storage and emerge with nr_frags == 0, so
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skb_has_shared_frag() returns false on its own; they need no change.
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Verified to apply with `patch -p1 -F0` (no offset, no fuzz, no rejects)
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against kernel-5.14.0-611.54.1.el9_7.
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The same omission exists in skb_gro_receive() and
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skb_gro_receive_list(). The former moves the incoming skb's frag
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descriptors into the accumulator's last sub-skb via two paths plus a
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"merge:" fallback that chains the whole skb onto frag_list; the
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latter chains the incoming skb whole onto p's frag_list. Downstream
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skb_segment() reads only skb_shinfo(p)->flags, and skb_segment_list()
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reuses each sub-skb's shinfo as the nskb -- both p and lp must carry
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the marker.
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Tree adaptation:
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* Upstream v3 places skb_gro_receive_list() in net/core/gro.c.
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AlmaLinux 9 still keeps it as a static helper in
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net/ipv4/udp_offload.c (it has not been promoted to a global
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GRO helper in this tree). Apply the propagation hunk there
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instead.
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* Upstream skb_shift() uses skb_len_add() helpers (introduced in
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v5.16); AlmaLinux 9 still has the open-coded
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`skb->len -= shiftlen; ...` block. The insertion point (right
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after both ip_summed assignments) is the same.
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Fixes: cef401de7be8 ("net: fix possible wrong checksum generation")
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Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags")
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Reported-by: Sultan Alsawaf <sultan@kerneltoast.com>
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Reported-by: William Bowling <vakzz@zellic.io>
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Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
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Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
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Signed-off-by: Eduard Abdullin <eabdullin@almalinux.org>
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---
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net/core/skbuff.c | 3 +++
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1 file changed, 3 insertions(+)
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net/core/gro.c | 2 ++
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net/core/skbuff.c | 6 ++++++
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net/ipv4/udp_offload.c | 2 ++
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3 files changed, 10 insertions(+)
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--- a/net/core/gro.c
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+++ b/net/core/gro.c
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@@ -222,10 +222,12 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
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p->data_len += len;
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p->truesize += delta_truesize;
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p->len += len;
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+ skb_shinfo(p)->flags |= skbinfo->flags & SKBFL_SHARED_FRAG;
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if (lp != p) {
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lp->data_len += len;
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lp->truesize += delta_truesize;
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lp->len += len;
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+ skb_shinfo(lp)->flags |= skbinfo->flags & SKBFL_SHARED_FRAG;
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}
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NAPI_GRO_CB(skb)->same_flow = 1;
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return 0;
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--- a/net/core/skbuff.c
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+++ b/net/core/skbuff.c
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@@ -2026,6 +2026,7 @@ struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom,
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@ -52,7 +89,16 @@ Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
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}
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if (skb_has_frag_list(skb)) {
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@@ -5740,6 +5741,8 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
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@@ -4029,6 +4030,8 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen)
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tgt->ip_summed = CHECKSUM_PARTIAL;
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skb->ip_summed = CHECKSUM_PARTIAL;
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+ skb_shinfo(tgt)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG;
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+
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/* Yak, is it really working this way? Some helper please? */
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skb->len -= shiftlen;
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skb->data_len -= shiftlen;
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@@ -5740,6 +5743,8 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
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from_shinfo->frags,
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from_shinfo->nr_frags * sizeof(skb_frag_t));
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to_shinfo->nr_frags += from_shinfo->nr_frags;
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@ -61,5 +107,16 @@ Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
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if (!skb_cloned(from))
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from_shinfo->nr_frags = 0;
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--- a/net/ipv4/udp_offload.c
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+++ b/net/ipv4/udp_offload.c
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@@ -487,6 +487,8 @@ static int skb_gro_receive_list(struct sk_buff *p, struct sk_buff *skb)
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p->truesize += skb->truesize;
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p->len += skb->len;
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+ skb_shinfo(p)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG;
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+
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NAPI_GRO_CB(skb)->same_flow = 1;
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return 0;
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--
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2.43.0
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@ -165,13 +165,13 @@ Summary: The Linux kernel
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# define buildid .local
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%define specversion 5.14.0
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%define patchversion 5.14
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%define pkgrelease 611.54.4
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%define pkgrelease 611.54.5
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%define kversion 5
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%define tarfile_release 5.14.0-611.54.1.el9_7
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# This is needed to do merge window version magic
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%define patchlevel 14
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# This allows pkg_release to have configurable %%{?dist} tag
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%define specrelease 611.54.4%{?buildid}%{?dist}
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%define specrelease 611.54.5%{?buildid}%{?dist}
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# This defines the kabi tarball version
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%define kabiversion 5.14.0-611.54.1.el9_7
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@ -3777,6 +3777,9 @@ fi
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#
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#
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%changelog
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* Thu May 14 2026 Eduard Abdullin <eabdullin@almalinux.org> - 5.14.0-611.54.5
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- net: skbuff: propagate shared-frag marker through frag-transfer helpers
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* Wed May 13 2026 Andrew Lukoshko <alukoshko@almalinux.org> - 5.14.0-611.54.4
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- net: skbuff: propagate shared-frag marker through pskb_copy()
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