CVE-2026-81010: io_uring/waitid: honor task_work cancellation

CVE-2026-81010: io_uring/waitid: honor task_work cancellation

[Greg Kroah-Hartman]

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

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

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

io_uring/waitid: honor task_work cancellation

io_waitid_cb() may run through the fallback task_work path when
task_work_add() can no longer queue work to the originating task. The
fallback runs from a kworker and io_uring marks such task work as
canceled through tw.cancel.

io_waitid_cb() currently ignores tw.cancel and calls __do_wait().
waitid is task-context dependent: __do_wait() performs child lookup
relative to current, and the retry path also uses
current->signal->wait_chldexit. If the callback runs from the fallback
kworker, current is therefore not the task that submitted the request.

Honor tw.cancel before entering __do_wait(). Complete the request with
-ECANCELED and skip the siginfo copy, since canceled task work may run
without the submitting task's userspace execution context.

Keep the existing siginfo handling for normal waitid completion and
explicit cancellation.

The Linux kernel CVE team has assigned CVE-2026-81010 to this issue.


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

	Issue introduced in 6.7 with commit f31ecf671ddc498f20219453395794ff2383e06b and fixed in 7.2.4 with commit 7bc98e2de8c58a2bfaf0f540eb096a386ecfc96c
	Issue introduced in 6.7 with commit f31ecf671ddc498f20219453395794ff2383e06b and fixed in 7.3-rc1 with commit 14572de82e5022899e5856008bc9cac97004a88c

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-2026-81010
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:
	io_uring/waitid.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/7bc98e2de8c58a2bfaf0f540eb096a386ecfc96c
	https://git.kernel.org/stable/c/14572de82e5022899e5856008bc9cac97004a88c