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Reapply Dirty Frag fixes (CVE-2026-43284, CVE-2026-43500) and add pskb_copy marker propagation

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Restore the two Dirty Frag patches that were introduced on this branch
in 6.12.0-226 (commit 2a779fc66) and dropped during the import of
6.12.0-227.el10:

  1100-xfrm-esp-avoid-in-place-decrypt-shared-skb-frags.patch
  1101-rxrpc-linearize-paged-frags.patch

Add the sibling supplement already shipped on the a10 branch as its
local Patch1100, renumbered to 1102 here so it sits next to the other
two:

  1102-net-skbuff-propagate-shared-frag-marker.patch

Release is not bumped; new entry is added under the existing
6.12.0-227 version, matching the pattern used by the original 226
commit.
This commit is contained in:
Andrew Lukoshko 2026-05-13 17:01:53 +00:00
parent 78087d1923
commit b3bdb38281
4 changed files with 221 additions and 0 deletions
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77
1100-xfrm-esp-avoid-in-place-decrypt-shared-skb-frags.patch Normal file
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@ -0,0 +1,77 @@
From: Andrew Lukoshko <alukoshko@almalinux.org>
Subject: [PATCH AlmaLinux 10] xfrm: esp: avoid in-place decrypt on shared skb frags
Direct cherry-pick of upstream commit f4c50a4034e6 for AlmaLinux 10
(6.12 kernel).
Verified to apply with `patch -p1 -F0` (no offset, no fuzz, no rejects)
against kernel-6.12.0-124.55.1.el10_1.
ESP-in-UDP packets built from MSG_SPLICE_PAGES (pipe pages) look like
ordinary uncloned nonlinear skbs to ESP input, which takes the no-COW
fast path and decrypts in place over data that is not owned privately
by the skb. Mark IPv4/IPv6 datagram splice frags with SKBFL_SHARED_FRAG
matching TCP, and make ESP input fall back to skb_cow_data() when the
flag is present.
Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
Fixes: 7da0dde68486 ("ip, udp: Support MSG_SPLICE_PAGES")
Fixes: 6d8192bd69bb ("ip6, udp6: Support MSG_SPLICE_PAGES")
(cherry picked from commit f4c50a4034e62ab75f1d5cdd191dd5f9c77fdff4)
Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
---
net/ipv4/esp4.c | 3 ++-
net/ipv4/ip_output.c | 2 ++
net/ipv6/esp6.c | 3 ++-
net/ipv6/ip6_output.c | 2 ++
4 files changed, 8 insertions(+), 2 deletions(-)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -908,7 +908,8 @@
nfrags = 1;
goto skip_cow;
- } else if (!skb_has_frag_list(skb)) {
+ } else if (!skb_has_frag_list(skb) &&
+ !skb_has_shared_frag(skb)) {
nfrags = skb_shinfo(skb)->nr_frags;
nfrags++;
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1236,6 +1236,8 @@
if (err < 0)
goto error;
copy = err;
+ if (!(flags & MSG_NO_SHARED_FRAGS))
+ skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG;
wmem_alloc_delta += copy;
} else if (!zc) {
int i = skb_shinfo(skb)->nr_frags;
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -950,7 +950,8 @@
nfrags = 1;
goto skip_cow;
- } else if (!skb_has_frag_list(skb)) {
+ } else if (!skb_has_frag_list(skb) &&
+ !skb_has_shared_frag(skb)) {
nfrags = skb_shinfo(skb)->nr_frags;
nfrags++;
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1769,6 +1769,8 @@
if (err < 0)
goto error;
copy = err;
+ if (!(flags & MSG_NO_SHARED_FRAGS))
+ skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG;
wmem_alloc_delta += copy;
} else if (!zc) {
int i = skb_shinfo(skb)->nr_frags;
--
2.43.0

69
1101-rxrpc-linearize-paged-frags.patch Normal file
View File

@ -0,0 +1,69 @@
From: Andrew Lukoshko <alukoshko@almalinux.org>
Subject: [PATCH AlmaLinux 10] rxrpc: linearize incoming DATA packet when it has paged frags
AlmaLinux-specific backport of the intent of the upstream rxrpc fix
posted at https://lore.kernel.org/all/afKV2zGR6rrelPC7@v4bel/ for the
"Dirty Frag" class of bugs (sibling to upstream commit f4c50a4034e6 in
the ESP/xfrm subsystem).
The upstream patch can not be cherry-picked against this 6.12 tree:
its target lines were introduced by upstream commit d0d5c0cd1e71
("rxrpc: Use skb_unshare() rather than skb_cow_data()") which is not
present here. The age-equivalent code path on AlmaLinux 10 is the
centralized skb_unshare() in net/rxrpc/io_thread.c that is run for
every DATA packet with a non-zero securityIndex before in-place
decryption.
skb_unshare() only handles cloned skbs. An skb that is non-cloned but
carries paged fragments (skb->data_len != 0) — e.g. pages attached via
udp_sendpage() / splice() / MSG_SPLICE_PAGES on a UDP socket carrying
rxrpc traffic — slips through and is decrypted in place over data the
skb does not own privately. With kernel-modules-partner installed
(rxrpc.ko enabled), this is exploitable.
Replace the unconditional skb_unshare() with skb_copy() whenever the
skb is cloned OR carries paged fragments. skb_copy() always returns a
freshly allocated linear skb, so subsequent in-place decryption only
touches kernel-owned memory. The original skb is consumed explicitly
(skb_unshare did this internally via consume_skb()).
Verified to apply with `patch -p1 -F0` (no offset, no fuzz, no
rejects) against kernel-6.12.0-124.55.1.el10_1.
Fixes: cac2661c53f3 ("rxrpc: Use skb_cow_data() in rxrpc_recvmsg_data()")
Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
---
net/rxrpc/io_thread.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
--- a/net/rxrpc/io_thread.c
+++ b/net/rxrpc/io_thread.c
@@ -235,16 +235,18 @@
* decryption.
*/
if (sp->hdr.securityIndex != 0) {
- skb = skb_unshare(skb, GFP_ATOMIC);
- if (!skb) {
- rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare_nomem);
- *_skb = NULL;
- return just_discard;
- }
+ if (skb_cloned(skb) || skb->data_len) {
+ struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
+
+ if (!nskb) {
+ rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare_nomem);
+ return just_discard;
+ }
- if (skb != *_skb) {
rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare);
- *_skb = skb;
+ consume_skb(*_skb);
+ *_skb = nskb;
+ skb = nskb;
rxrpc_new_skb(skb, rxrpc_skb_new_unshared);
sp = rxrpc_skb(skb);
}
--
2.43.0

64
1102-net-skbuff-propagate-shared-frag-marker.patch Normal file
View File

@ -0,0 +1,64 @@
From: Andrew Lukoshko <alukoshko@almalinux.org>
Subject: [PATCH AlmaLinux 10] net: skbuff: propagate shared-frag marker through pskb_copy()
Backport of upstream patch posted at
https://lore.kernel.org/all/agRfuVOeMI5pbHhY@v4bel/
(sibling to the xfrm/esp shared-frag fix upstream commit f4c50a4034e6,
already merged into 6.12.0-124.56.1 via the c10s import).
__pskb_copy_fclone() shallow-copies the source's frag descriptors and
bumps each page's refcount via skb_frag_ref(), then defers the rest
of the shinfo metadata to skb_copy_header(). That helper only carries
over gso_{size,segs,type} and never touches skb_shinfo()->flags, so
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.
Verified to apply with `patch -p1 -F0` (no offset, no fuzz, no rejects)
against kernel-6.12.0-124.56.1.el10_1.
Fixes: cef401de7be8 ("net: fix possible wrong checksum generation")
Fixes: f4c50a4034e6 ("xfrm: esp: avoid in-place decrypt on shared skb frags")
Reported-by: William Bowling <vakzz@zellic.io>
Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
---
net/core/skbuff.c | 3 +++
1 file changed, 3 insertions(+)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2123,6 +2123,7 @@ 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)) {
@@ -6028,6 +6029,8 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
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;
--
2.43.0

11
kernel.spec
View File

@ -1143,6 +1143,9 @@ Patch2007: 0007-Bring-back-deprecated-pci-ids-to-be2iscsi-driver.patch
Patch2008: 0008-Bring-back-deprecated-pci-ids-to-megaraid_sas-driver.patch
Patch2009: 0009-Bring-back-deprecated-pci-ids-to-mpt3sas-driver.patch
Patch2010: 0001-Keep-fs-btrfs-files-in-modules-package.patch
Patch1100: 1100-xfrm-esp-avoid-in-place-decrypt-shared-skb-frags.patch
Patch1101: 1101-rxrpc-linearize-paged-frags.patch
Patch1102: 1102-net-skbuff-propagate-shared-frag-marker.patch
# END OF PATCH DEFINITIONS
@ -2038,6 +2041,9 @@ ApplyPatch 0007-Bring-back-deprecated-pci-ids-to-be2iscsi-driver.patch
ApplyPatch 0008-Bring-back-deprecated-pci-ids-to-megaraid_sas-driver.patch
ApplyPatch 0009-Bring-back-deprecated-pci-ids-to-mpt3sas-driver.patch
ApplyPatch 0001-Keep-fs-btrfs-files-in-modules-package.patch
ApplyPatch 1100-xfrm-esp-avoid-in-place-decrypt-shared-skb-frags.patch
ApplyPatch 1101-rxrpc-linearize-paged-frags.patch
ApplyPatch 1102-net-skbuff-propagate-shared-frag-marker.patch
%{log_msg "End of patch applications"}
# END OF PATCH APPLICATIONS
@ -4552,6 +4558,11 @@ fi\
#
#
%changelog
* Wed May 13 2026 Andrew Lukoshko <alukoshko@almalinux.org> - 6.12.0-227
- xfrm: esp: avoid in-place decrypt on shared skb frags (CVE-2026-43284)
- rxrpc: linearize incoming DATA packet when it has paged frags (CVE-2026-43500)
- net: skbuff: propagate shared-frag marker through pskb_copy()
* Wed May 13 2026 Eduard Abdullin <eabdullin@almalinux.org> - 6.12.0-227
- Debrand for AlmaLinux OS
- Use AlmaLinux OS secure boot cert