CVE-2026-46331: net/sched: fix pedit partial COW leading to page cache corruption

CVE-2026-46331: net/sched: fix pedit partial COW leading to page cache corruption

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net/sched: fix pedit partial COW leading to page cache corruption

tcf_pedit_act() computes the COW range for skb_ensure_writable()
once before the key loop using tcfp_off_max_hint, but the hint does
not account for the runtime header offset added by typed keys. This
can leave part of the write region un-COW'd.

Fix by moving skb_ensure_writable() inside the per-key loop where
the actual write offset is known, and add overflow checking on the
offset arithmetic. For negative offsets (e.g. Ethernet header edits
at ingress), use skb_cow() to COW the headroom instead. Guard
offset_valid() against INT_MIN, where negation is undefined.

The Linux kernel CVE team has assigned CVE-2026-46331 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.18 with commit 8b796475fd7882663a870456466a4fb315cc1bd6 and fixed in 7.1 with commit 899ee91156e57784090c5565e4f31bd7dbffbc5a
	Issue introduced in 4.19.244 with commit d0c38a914b0c4c21d553da801003d36979016726
	Issue introduced in 5.4.195 with commit 2ec2dd7d51a9320151f275ddbb2b53260fb32ca1
	Issue introduced in 5.10.117 with commit abe35bf3be51482593076d516a680d79e5fbc8e1
	Issue introduced in 5.15.41 with commit b773640d5bb9e2acfd91e2695717af04d47aa116
	Issue introduced in 5.17.9 with commit c19cc520b3d69904e9518d401ad0df7f4702aca0

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-46331
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	include/net/tc_act/tc_pedit.h
	net/sched/act_pedit.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/899ee91156e57784090c5565e4f31bd7dbffbc5a