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Date: Tue, 24 May 2022 09:10:37 -0700
From: Kyle Zeng <zengyhkyle@...il.com>
To: oss-security@...ts.openwall.com
Subject: CVE-2022-1786: Linux Kernel invalid-free in io_uring
Hi there,
I recently found a severe invalid-free bug in the io_uring subsystem
which affects Linux kernel v5.10. It has been demonstrated that the
vulnerability can be exploited to achieve local privilege escalation.
# Root Cause
The root cause of the bug is a misuse of the identity model in
io_uring. When preparing a request, the kernel uses the identity of
the current task instead of that of the request task, which causes
type confusion and invalid-free when the request needs to be
destroyed.
# Impact
I wrote a proof-of-concept exploit and demonstrated that it can be
used to achieve local privilege escalation.
# Affected Versions
To the best of my knowledge, this bug only affects Linux kernel v5.10
and v5.11 because of their unique identity model in io_uring. But it
still affects many users because of some widely used vendors (Android
12, ChromeOS, etc).
# Disclosure & Patch
I already contacted the Linux security team and prepared a patch. The
patch has been merged into the Linux kernel stable tree and it can be
found here: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.10.y&id=29f077d070519a88a793fbc70f1e6484dc6d9e35.
I also informed the vendors and gave enough time for them to patch the
bug before this public disclosure.
--
Kyle Zeng
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