CVE-2026-72426: bpf: Preserve pointer spill metadata during half-slot cleanup

CVE-2026-72426: bpf: Preserve pointer spill metadata during half-slot cleanup

[Greg Kroah-Hartman]

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

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

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

bpf: Preserve pointer spill metadata during half-slot cleanup

__clean_func_state() cleans dead stack slots in 4-byte halves. When the
high half of a STACK_SPILL slot is dead and the low half remains live,
cleanup converts the live low half to STACK_MISC or STACK_ZERO and clears
the saved spilled_ptr metadata.

That conversion is safe only for scalar spills. For a pointer spill, this
metadata clear lets a later 32-bit fill from the still-live half avoid the
normal non-scalar register-fill check and be treated as an ordinary scalar
stack read.

Leave non-scalar spill slots intact in this half-live shape. This is
conservative for pruning and preserves the existing
check_stack_read_fixed_off() rejection path for partial fills from pointer
spills.

The Linux kernel CVE team has assigned CVE-2026-72426 to this issue.


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

	Issue introduced in 7.1 with commit be23266b4a08540aa43d8503a2ea10247c8daebe and fixed in 7.1.5 with commit 0f9278b22cda6fd2525049930157b79b4036b4ef
	Issue introduced in 7.1 with commit be23266b4a08540aa43d8503a2ea10247c8daebe and fixed in 7.2-rc1 with commit 3a354149bceacadbcf7d7b4766f5ef26a85892ab

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-2026-72426
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:
	kernel/bpf/states.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/0f9278b22cda6fd2525049930157b79b4036b4ef
	https://git.kernel.org/stable/c/3a354149bceacadbcf7d7b4766f5ef26a85892ab