CVE-2026-72110: bpf,fork: wipe ->bpf_storage before bailouts that access it

From: Greg Kroah-Hartman <[email protected]>

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

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

bpf,fork: wipe ->bpf_storage before bailouts that access it

Currently, copy_process() can bail out to free_task() before p->bpf_storage
has been initialized, with this call graph (shown here for the
!CONFIG_MEMCG case):

copy_process
  dup_task_struct
    arch_dup_task_struct
      [copies the entire task_struct, including ->bpf_storage member]
  [RLIMIT_NPROC check fails]
  delayed_free_task
    free_task
      bpf_task_storage_free
        rcu_dereference(task->bpf_storage)
        bpf_local_storage_destroy

In this case, the nascent task's ->bpf_storage member that
bpf_local_storage_destroy() operates on is a plain copy of the parent's
->bpf_storage pointer, not a real initialized pointer.
This leads to badness (kernel hangs, UAF).

This is reachable as long as the process calling fork() has been inserted
into a task storage map.

The Linux kernel CVE team has assigned CVE-2026-72110 to this issue.


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

	Issue introduced in 5.13 with commit a10787e6d58c24b51e91c19c6d16c5da89fcaa4b and fixed in 6.6.145 with commit c3fd6f28c7ce1142a3b23dbb840eaa4777de1d74
	Issue introduced in 5.13 with commit a10787e6d58c24b51e91c19c6d16c5da89fcaa4b and fixed in 6.12.97 with commit 9cff220ddb65b022cc668bb652200742476e744c
	Issue introduced in 5.13 with commit a10787e6d58c24b51e91c19c6d16c5da89fcaa4b and fixed in 6.18.40 with commit c4f626ddf2350652ad2f79daf1f10847f3f6eabd
	Issue introduced in 5.13 with commit a10787e6d58c24b51e91c19c6d16c5da89fcaa4b and fixed in 7.1.5 with commit 43f0005f81b8ce3be962d653cde8db9022f1e9b0
	Issue introduced in 5.13 with commit a10787e6d58c24b51e91c19c6d16c5da89fcaa4b and fixed in 7.2-rc2 with commit 9b51a6155d14389876916726430da30eabb1d4ed

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-2026-72110
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/fork.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/c3fd6f28c7ce1142a3b23dbb840eaa4777de1d74
	https://git.kernel.org/stable/c/9cff220ddb65b022cc668bb652200742476e744c
	https://git.kernel.org/stable/c/c4f626ddf2350652ad2f79daf1f10847f3f6eabd
	https://git.kernel.org/stable/c/43f0005f81b8ce3be962d653cde8db9022f1e9b0
	https://git.kernel.org/stable/c/9b51a6155d14389876916726430da30eabb1d4ed