CVE-2026-99263: io_uring/poll: avoid retry wakeup loss when dropping ownership

CVE-2026-99263: io_uring/poll: avoid retry wakeup loss when dropping ownership

[Greg Kroah-Hartman]

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

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

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

io_uring/poll: avoid retry wakeup loss when dropping ownership

If a wakeup sets IO_POLL_RETRY_FLAG between the owning task consuming
the existing instance of IO_POLL_RETRY_FLAG and the loop check
of io_poll_check_events(), then we stall on processing the request
until an unrelated wakeup comes along.

Using atomic_cmpxchg instead of atomic_sub_return to guarantee both the
count v and poll_refs are 0 and no wake-ups are missed.

The Linux kernel CVE team has assigned CVE-2026-99263 to this issue.


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

	Issue introduced in 6.1 with commit a26a35e9019fd70bf3cf647dcfdae87abc7bacea and fixed in 6.1.191 with commit d1f6850086ac6f8b0fa44fb19aa2a468c73ee071
	Issue introduced in 6.1 with commit a26a35e9019fd70bf3cf647dcfdae87abc7bacea and fixed in 6.6.161 with commit 41fae2e9e1fa3bee86aee0a25ba90e59ce5024bf
	Issue introduced in 6.1 with commit a26a35e9019fd70bf3cf647dcfdae87abc7bacea and fixed in 6.12.115 with commit 4ef685b8505615729d75c875f52822238bf76ca6
	Issue introduced in 6.1 with commit a26a35e9019fd70bf3cf647dcfdae87abc7bacea and fixed in 6.18.60 with commit afa407c02f3aa0fd872f86c9bf1b34502e0fa8f0
	Issue introduced in 6.1 with commit a26a35e9019fd70bf3cf647dcfdae87abc7bacea and fixed in 7.2.14 with commit eb2a50d8235e4580fea9aa20f3fbe1a002c38cb1
	Issue introduced in 6.1 with commit a26a35e9019fd70bf3cf647dcfdae87abc7bacea and fixed in 7.3.1 with commit 521e8a65e9b45532295ba1082ef12be6e80c173b
	Issue introduced in 5.15.82 with commit 4b702b7d11ce1b9d26fc6d7c5a7ef4ac1d455048
	Issue introduced in 6.0.11 with commit bc4e6ee16778149811333a969a7a893d4cc110c5

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-2026-99263
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/poll.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/d1f6850086ac6f8b0fa44fb19aa2a468c73ee071
	https://git.kernel.org/stable/c/41fae2e9e1fa3bee86aee0a25ba90e59ce5024bf
	https://git.kernel.org/stable/c/4ef685b8505615729d75c875f52822238bf76ca6
	https://git.kernel.org/stable/c/afa407c02f3aa0fd872f86c9bf1b34502e0fa8f0
	https://git.kernel.org/stable/c/eb2a50d8235e4580fea9aa20f3fbe1a002c38cb1
	https://git.kernel.org/stable/c/521e8a65e9b45532295ba1082ef12be6e80c173b
	https://git.kernel.org/stable/c/937d38dcacd675dc0572d6c9b6743960df3128ed