CVE-2026-64075: fprobe: Fix unregister_fprobe() to wait for RCU grace period

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

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

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

fprobe: Fix unregister_fprobe() to wait for RCU grace period

Commit 4346ba1604093 ("fprobe: Rewrite fprobe on function-graph tracer")
changed fprobe to register struct fprobe to an rcu-hlist, but it forgot
to wait for RCU GP. Thus there can be use-after-free if the fprobe is
released right after unregistering. This can be happened on fprobe
event and sample module code.

To fix this issue, add synchronize_rcu() in unregister_fprobe().

Note that BPF is OK because fprobe is used as a part of
bpf_kprobe_multi_link. This unregisters its fprobe in
bpf_kprobe_multi_link_release() and it is deallocated via
bpf_kprobe_multi_link_dealloc(), which is invoked from
bpf_link_defer_dealloc_rcu_gp() RCU callback.

For BPF, this also introduced unregister_fprobe_async() which does
NOT wait for RCU grace priod.

The Linux kernel CVE team has assigned CVE-2026-64075 to this issue.


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

	Issue introduced in 6.14 with commit 4346ba1604093305a287e08eb465a9c15ba05b80 and fixed in 6.18.34 with commit 56b4cfcf1518245493c60fd39c56978f508f1816
	Issue introduced in 6.14 with commit 4346ba1604093305a287e08eb465a9c15ba05b80 and fixed in 7.0.11 with commit a4f6a9005ed6cfd360ef2520430927f05f92ffb0
	Issue introduced in 6.14 with commit 4346ba1604093305a287e08eb465a9c15ba05b80 and fixed in 7.1 with commit 657b594b2084b39a4bc6d8493aa2140cb00cea49

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-2026-64075
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/linux/fprobe.h
	kernel/trace/bpf_trace.c
	kernel/trace/fprobe.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/56b4cfcf1518245493c60fd39c56978f508f1816
	https://git.kernel.org/stable/c/a4f6a9005ed6cfd360ef2520430927f05f92ffb0
	https://git.kernel.org/stable/c/657b594b2084b39a4bc6d8493aa2140cb00cea49