linux-cve-announce - CVE-2025-21633: io_uring/sqpoll: zero sqd->thread on tctx errors

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Message-ID: <2025011942-CVE-2025-21633-a313@gregkh>
Date: Sun, 19 Jan 2025 11:17:42 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21633: io_uring/sqpoll: zero sqd->thread on tctx errors

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

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

io_uring/sqpoll: zero sqd->thread on tctx errors

Syzkeller reports:

BUG: KASAN: slab-use-after-free in thread_group_cputime+0x409/0x700 kernel/sched/cputime.c:341
Read of size 8 at addr ffff88803578c510 by task syz.2.3223/27552
 Call Trace:
  <TASK>
  ...
  kasan_report+0x143/0x180 mm/kasan/report.c:602
  thread_group_cputime+0x409/0x700 kernel/sched/cputime.c:341
  thread_group_cputime_adjusted+0xa6/0x340 kernel/sched/cputime.c:639
  getrusage+0x1000/0x1340 kernel/sys.c:1863
  io_uring_show_fdinfo+0xdfe/0x1770 io_uring/fdinfo.c:197
  seq_show+0x608/0x770 fs/proc/fd.c:68
  ...

That's due to sqd->task not being cleared properly in cases where
SQPOLL task tctx setup fails, which can essentially only happen with
fault injection to insert allocation errors.

The Linux kernel CVE team has assigned CVE-2025-21633 to this issue.

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

	Issue introduced in 6.9 with commit 1251d2025c3e1bcf1f17ec0f3c0dfae5e5bbb146 and fixed in 6.12.10 with commit aa7496d668c30ca7421b3bfdcd948ee861a13d17
	Issue introduced in 6.9 with commit 1251d2025c3e1bcf1f17ec0f3c0dfae5e5bbb146 and fixed in 6.13-rc7 with commit 4b7cfa8b6c28a9fa22b86894166a1a34f6d630ba

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-2025-21633
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/sqpoll.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/aa7496d668c30ca7421b3bfdcd948ee861a13d17
	https://git.kernel.org/stable/c/4b7cfa8b6c28a9fa22b86894166a1a34f6d630ba