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Date: Tue, 18 Oct 2022 13:59:51 -0300
From: Thadeu Lima de Souza Cascardo <>
Subject: CVE-2022-2602 - Linux kernel io_uring UAF

A local privilege escalation vulnerabilty involving Unix socket Garbage
Collection and io_uring was reported and fixed as:

0091bfc81741b8d3aeb3b7ab8636f911b2de6e80 ("io_uring/af_unix: defer registered files gc to io_uring release")

The vulnerability is a use-after-free that happens when an io_uring request
is being processed on a registered file and the Unix GC runs and frees the
io_uring fd and all the registered fds. The order at which the Unix GC
processes the inflight fds may lead to registered fds be freed before the
io_uring is released and has the chance to unregister and wait for such
requests to finish.

One way to trigger this race condition is to use userfaultfd and other
similar strategies that cause the request to be held waiting for the
attacker to trigger the free.

This issue was reported as ZDI-CAN-17428 and has been assigned

It affects upstream stable 5.4.y, 5.15.y and later versions. 5.10.y may be
mitigated by the fact that commit 0f2122045b946241a9e549c2a76cea54fa58a7ff
("io_uring: don't rely on weak ->files references") is present, but it is
safer to apply the fixes.

A PoC will be posted in 7 days, on October 25th.


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