CVE-2026-68334: rxrpc: fix io_thread race in rxrpc_wake_up_io_thread()

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

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

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

rxrpc: fix io_thread race in rxrpc_wake_up_io_thread()

rxrpc_wake_up_io_thread() checks local->io_thread before waking it, but
then reloads the pointer for wake_up_process().

local->io_thread is cleared with WRITE_ONCE() when the I/O thread exits, so
the second load can see NULL even if the first load did not.

Take a READ_ONCE() snapshot and use it for both the NULL check and the
wake_up_process() call, as rxrpc_encap_rcv() already does.

The Linux kernel CVE team has assigned CVE-2026-68334 to this issue.


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

	Issue introduced in 6.16 with commit 5800b1cf3fd8ccab752a101865be1e76dac33142 and fixed in 6.18.42 with commit c9165e199f56997f2f2deb5d3ec2dfab98dfa288
	Issue introduced in 6.16 with commit 5800b1cf3fd8ccab752a101865be1e76dac33142 and fixed in 7.1.6 with commit 092b42cf3f6013eec43607ecbcad674723649514
	Issue introduced in 6.16 with commit 5800b1cf3fd8ccab752a101865be1e76dac33142 and fixed in 7.2-rc5 with commit 745fb794c3e933c023af9dbb5876a5e16ad2dc71

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-2026-68334
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/rxrpc/ar-internal.h


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/c9165e199f56997f2f2deb5d3ec2dfab98dfa288
	https://git.kernel.org/stable/c/092b42cf3f6013eec43607ecbcad674723649514
	https://git.kernel.org/stable/c/745fb794c3e933c023af9dbb5876a5e16ad2dc71