Andrew Lukoshko
01f79da1ca
Bring back three local patches that were dropped from a9 after upstream landed the related fixes. The xfrm-esp fix (CVE-2026-43284) came in via the CKI Backport Bot at 5.14.0-611.55.1, but rxrpc, net/skbuff and ptrace did not -- restore them here. Blobs are imported verbatim from the latest a9 commits that carried them (2530dd40b/d62b1833b/cbd86e459/cc48c27cd): 1101-rxrpc-linearize-paged-frags.patch (CVE-2026-43500) 1102-net-skbuff-propagate-shared-frag-marker.patch v3 frag-transfer helpers variant (CVE-2026-46300 "Fragnesia") 1103-ptrace-require-cap-on-mm-less-task.patch CVE-2026-46333, kABI-safe replacement for upstream 31e62c2ebbfd Release is not bumped; a second changelog entry is added under the existing 5.14.0-611.55.1 version. All three verified to apply with `patch -p1 -F0` against the 5.14.0-611.55.1.el9_7 source tree (one minor offset, no fuzz, no rejects).
123 lines
4.9 KiB
Diff
123 lines
4.9 KiB
Diff
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 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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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). 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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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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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: Eduard Abdullin <eabdullin@almalinux.org>
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---
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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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skb_frag_ref(skb, i);
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}
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skb_shinfo(n)->nr_frags = i;
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+ skb_shinfo(n)->flags |= skb_shinfo(skb)->flags & SKBFL_SHARED_FRAG;
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}
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if (skb_has_frag_list(skb)) {
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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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+ if (from_shinfo->nr_frags)
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+ to_shinfo->flags |= from_shinfo->flags & SKBFL_SHARED_FRAG;
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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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