CVE-2026-45927: bpf: Require frozen map for calculating map hash

CVE-2026-45927: bpf: Require frozen map for calculating map hash

[Greg Kroah-Hartman]

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

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

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

bpf: Require frozen map for calculating map hash

Currently, bpf_map_get_info_by_fd calculates and caches the hash of the
map regardless of the map's frozen state.

This leads to a TOCTOU bug where userspace can call
BPF_OBJ_GET_INFO_BY_FD to cache the hash and then modify the map
contents before freezing.

Therefore, a trusted loader can be tricked into verifying the stale hash
while loading the modified contents.

Fix this by returning -EPERM if the map is not frozen when the hash is
requested. This ensures the hash is only generated for the final,
immutable state of the map.

The Linux kernel CVE team has assigned CVE-2026-45927 to this issue.


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

	Issue introduced in 6.18 with commit ea2e6467ac36bf3d785defc89e58269b15d182f7 and fixed in 6.18.14 with commit 7752d36343862323bbeea4ce3adf0ec2ed86e122
	Issue introduced in 6.18 with commit ea2e6467ac36bf3d785defc89e58269b15d182f7 and fixed in 6.19.4 with commit f415e114b58fe02c41191e47f24bdabb438daf72
	Issue introduced in 6.18 with commit ea2e6467ac36bf3d785defc89e58269b15d182f7 and fixed in 7.0 with commit a2c86aa621c22f2a7e26c654f936d65cfff0aa91

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-2026-45927
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/syscall.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/7752d36343862323bbeea4ce3adf0ec2ed86e122
	https://git.kernel.org/stable/c/f415e114b58fe02c41191e47f24bdabb438daf72
	https://git.kernel.org/stable/c/a2c86aa621c22f2a7e26c654f936d65cfff0aa91