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Bump version to 6.12.0-124.56.2

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net: skbuff: propagate shared-frag marker through pskb_copy()

Sibling fix to upstream commit f4c50a4034e6 ("xfrm: esp: avoid
in-place decrypt on shared skb frags") which is already part of the
124.56.1 rebase. __pskb_copy_fclone() and skb_try_coalesce()
shallow-copied frag descriptors without propagating SKBFL_SHARED_FRAG,
so destinations referencing externally-owned pages reported
skb_has_shared_frag() as false. Combined with an nft 'dup to <local>'
rule (or any other nf_dup_ipv4 / xt_TEE caller), this lets an
unprivileged user write into the page cache of a root-owned read-only
file via ESP-input in-place decryption.

Backport of https://lore.kernel.org/all/agRfuVOeMI5pbHhY@v4bel/
This commit is contained in:
Andrew Lukoshko 2026-05-13 13:18:59 +00:00 committed by Andrew Lukoshko
parent 0beec5c537
commit c3f0a68cfa
2 changed files with 71 additions and 2 deletions
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64
1100-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

9
kernel.spec
View File

@ -176,13 +176,13 @@ Summary: The Linux kernel
%define specrpmversion 6.12.0
%define specversion 6.12.0
%define patchversion 6.12
%define pkgrelease 124.56.1
%define pkgrelease 124.56.2
%define kversion 6
%define tarfile_release 6.12.0-124.56.1.el10_1
# This is needed to do merge window version magic
%define patchlevel 12
# This allows pkg_release to have configurable %%{?dist} tag
%define specrelease 124.56.1%{?buildid}%{?dist}
%define specrelease 124.56.2%{?buildid}%{?dist}
# This defines the kabi tarball version
%define kabiversion 6.12.0-124.56.1.el10_1
@ -1128,6 +1128,7 @@ 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: 0010-Bring-back-deprecated-pci-ids-to-aacraid-driver.patch
Patch1100: 1100-net-skbuff-propagate-shared-frag-marker.patch
# END OF PATCH DEFINITIONS
@ -1989,6 +1990,7 @@ 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 0010-Bring-back-deprecated-pci-ids-to-aacraid-driver.patch
ApplyPatch 1100-net-skbuff-propagate-shared-frag-marker.patch
%{log_msg "End of patch applications"}
# END OF PATCH APPLICATIONS
@ -4377,6 +4379,9 @@ fi\
#
#
%changelog
* Wed May 13 2026 Andrew Lukoshko <alukoshko@almalinux.org> - 6.12.0-124.56.2
- net: skbuff: propagate shared-frag marker through pskb_copy()
* Wed May 13 2026 Eduard Abdullin <eabdullin@almalinux.org> - 6.12.0-124.56.1
- Debrand for AlmaLinux OS
- Use AlmaLinux OS secure boot cert