CVE-2026-68399: bpf: Fix UAF in sock clone early bailouts

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

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

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

bpf: Fix UAF in sock clone early bailouts

Similar to recent commit 9b51a6155d14 ("bpf,fork: wipe ->bpf_storage
before bailouts that access it"), sk_clone() performs an initial
shallow copy of the socket field ->sk_bpf_storage via sock_copy()
for the cloned socket newsk.

If sk_clone() bails out early (e.g. if sk_filter_charge() fails) prior
to calling bpf_sk_storage_clone(), newsk->sk_bpf_storage still points
to the parent socket's BPF local storage. When newsk is subsequently
freed via sk_free(), the deallocation path (__sk_destruct() ->
bpf_sk_storage_free()) destroys the parent socket's BPF local storage,
leading to a use-after-free (UAF) on the parent socket.

Fix this by resetting newsk->sk_bpf_storage to NULL immediately after
sock_copy() in sk_clone(), and remove the now redundant initialization
from bpf_sk_storage_clone().

The Linux kernel CVE team has assigned CVE-2026-68399 to this issue.


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

	Issue introduced in 5.2 with commit 6ac99e8f23d4b10258406ca0dd7bffca5f31da9d and fixed in 7.1.6 with commit 14b49b5ab29979552c219a09e569b424fbbf4a6e
	Issue introduced in 5.2 with commit 6ac99e8f23d4b10258406ca0dd7bffca5f31da9d and fixed in 7.2-rc4 with commit 7cbd0c4cebe4c9f678d15e6b9ba975e1155a107f

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-2026-68399
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:
	net/core/bpf_sk_storage.c
	net/core/sock.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/14b49b5ab29979552c219a09e569b424fbbf4a6e
	https://git.kernel.org/stable/c/7cbd0c4cebe4c9f678d15e6b9ba975e1155a107f